It´s just that some natives do not find it enough or even do not recognise the passive meaning and add another passive suffix.

Grammatically correct way:

de-n-mek is the passive of de-mek

söyle-n-mek is the passive of söyle-mek

etc.

I usually do not read translation forum. So they naturally go unnoticed by me.

Illogical forms appear in every language. The question is when they are accepted into standard language. At some point usually language planners give up. What was the name of the Turkish language authorities´ board again? Do they have a web site? (Just for interest...)

I have an explanation for this situation. Most of the time we make a verb passive adding (i)l suffix. Ex: git - il - di. So I think some people subconsciously think only (i)l suffix make verbs passive and they think "n" as a buffer letter. So they add (i)l after n. So Abla you see even the irregularities in Turkish have a logic. 

It seems you are right, gokuyum. A very quick search brought up double passives for verbs like

         uyunmak (>*uyunulmak)

         beklenmek (>*beklenilmek)

         beslenmek   (>*beslenilmek).

Obviously it has something to do with the passive marking –n which speakers feel is “not enough” or something.

But not all double passive forms ended up in the dictionary like denilmek did. This is only a guess from me but maybe the connection with demek is easier to forget because of the irregularities in its stem vowels and that’s why the more regular (and yet one syllable) den- is considered the imaginary basis of the passive form.

The passive form of a Turkish verb is formed by adding (-ı,-i,-u,-ü l/n to its root or stem:

1) We add -ıl,-il,-ul,-ül to the verbs end in a consonant:

otur.ul, san.ıl, bak.ıl, çoğalt.ıl, iç.il, göm.ül, ban.ıl, kap.ıl, ser.il, as.ıl, it.il, ay,ıl, kaz.ıl, sev,il, sağ,ıl

l is exception (-ın,-in,-un,-ün):

kıl.ın, bil.in, gül.ün, bul.un

2) We add -n to the verbs end in a vowel: 

söyle.n, ara.n, oku.n, de.n, yıka.n

We also use the same suffixes to make reflexive form of some exact verbs.

For example yıkan can be both passive and reflexive.. please, study the examples below:

Ali yıkandı ve giyindi (both verbs are reflexive)

Ölü yıkandı ve gömüldü(both verbs are passive) 

The verbs that are originally reflexive  (kop, bat, etc) have no passive form.

But you can see people adding (passive)-il to a word which is already suffixed by (reflexive)-(i)n or -(i)n which is not clear enough if it is passive:

yıka.n.ıl, giy.in.il, söyle.n.il, de.n.il etc.

So the combination is: reflexive+passive (not passive+passive)

The question is: is this combination grammatically correct?

I am not sure if it is totally incorrect..

Which one sounds better to the native speakers?

a) böyle de giyinmez ki

b) böyle de giyinilmez ki

?

note: any addition, contribution or objection is welcomed.

Interesting. Two ways to see it. Which means it was maybe not a totally stupid idea to suspect a reflexive marking in the verb in the first place.

Reflexive: Agent=Patient. How can you make a passive out of it?

This is a tough one. I am not sure I know. But it has to do with the impersonal usage of Turkish passive which is a special feature of it. Of course I would miss it completely is there wasn´t a similar thing in Finnish. That´s why I understand completely when scalpel says

         yıka|n|ıl|dı = ´wash´ + ´himself´ + ´is done´ + ´sometimes in the past´.

(Well, this is not what he said but this is how I understood it.)

In Finnish it would be

         pese|ydy|t|ti|in = ´wash´ + ´self´ + ´is done´ + ´sometimes in the past´ + poss sg 3rd,

which means some people (probably more than one) washed themselves in the past. This is our passive. It can be formed from intransive verbs as well as transitive. It is used for reflexives as well. When we use impersonal passive we always mean that some people did the action, we just don´t know who.

Geoffrey Lewis writes: "The most remarkable feature of the Turkish passive is its impersonal use: niçin yalan söyle-n-ir? ´why are lies told?, i.e. ´why do people tell lies?´ In this example the passive verb appears to have a subject, but impersonal passives are also regularly formed from intransitive verbs and then have no conceivable grammatical subject..."

I also like the Wikipedia article about impersonal passive. There are some Turkish and German examples there.

Taking the risk of talking to myself I still want to stress that what I just wrote was only an answer to si++´s question. Yes, in world languages reflexive and passive markings can live just fine in the same verb when we talk about impersonal passive. And passive voice does have impersonal use in Turkish. That´s all.

What comes to the original question about what these odd verb forms really consist of naturally I won´t even try to answer it. It is for the natives to take or leave.

Well, I have given a thought to it and have some explaination now.

söylendi = he told something(s) to himself (reflexive but we have another object here)

so

söylenildi = something(s) was/were told by him to himself.

yıkandı = he washed himself (reflexive)

now let´s try with some adverbs in it.

nehirde yıkandı = he washed himself in the river

now we don´t say something like this:

nehir yıkanıldı (instead we say "nehirde yıkanıldı")

but impersonally

(içinde) yıkanılan nehir = the river in which they wash themselves

(or liretally the river in which they are washed by themselves)

According to the definition ("decreases the valency of an intransitive verb to zero")

         (Nehirde) yıkanıldı

is an impersonal passive.

The red text is not clear to me. Where is that definition from?

Nehirde yıkanılır may be impersonal and should mean:

one washes oneself in the river.

But when I say "nehirde yıkanıldı" I think I point out to a specific event performed by known (specific) people and it should mean:

they were washed by themselves in the river.

Or

şu anda nehirde yakanılıyor = they are washed by themselves in the river at this moment.

What exactly do you mean by impersonal passive?

Edit:

Never mind I have located the wikipedia page:

http://en.wikipedia.org/wiki/Impersonal_passive_voice

You can find the definition for instance in the Wikipedia article

         Impersonal Passive.

The valency of a transitive verb is usually two: it needs a subject and an object. The valency of an intransitive verb is usually one: It doesn´t need but a subject. The definition talks about this latter type. Impersonal passive changes an intransitive verb (whose valency is normally one) so that it doesn´t need either a subject or an object to be a grammatically acceptable sentence. Just like yıkanıldı in your example.

The meaning of an impersonal passive is different from the classical Latin passive. When impersonal is used it always means that some people (the speaker doesn´t know or care who) are performing the action. Always some people. Just like you described the meaning of your sentence.

I don´t claim Turkish passive is completely an impersonal but it has usage which can be defined impersonal.

I remember my professor always started his passive lectures with the same words: "Remember, in Finnish (sorry, again) we don´t actually have a passive, we have an impersonal." At this point I was fighting to keep my eyes open. Only after beginning to study Turkish I actually understood what the old man was saying.

Everytime I learn something I realise how little I know!

Unergative verb, unaccusative verb etc.etc.

However the Turkish example from the wikipedia page, which is said to be invalid sounds OK to me.

The verb ölmek "to die", however, is unaccusative and may not be passivized:

*Burada öl-ün-ür. (I think this is OK. It should mean "this is the place where you can die")

here die-PASS-PRESENT

"Here it is died."

Yep, it´s beautiful. New worlds open.

But yıkanmak is not an intransitive verb but reflexive. I would think it as a (special kind of) transitive where the object = the subject. The English translation helps to reveal the object:

yıkandı = he washed himself

A reflexive has a logical object, of course, but still the syntactic valency is like that of any intransitive verb. One. In agglutinative languages the reflexive marking (sort of) makes transitive verbs intransitive from the syntactic point of view.

It is a real pleasure to discuss these things with someone like you who has a great skill in language/grammar..  

yıkanıldı has exactly the same meaning as peseydyttiin does in Finnish: ´some people (probably more than one) washed themselves in the past.´

To the contrary of what some people may think, reflexive and passive are different things and a reflexive verb can have its passive form when necessary.

Remember the example I gave in my previous post:

a) Böyle de giyinmez ki (reflexive)

b) Böyle de giyinilmez ki (reflexive+passive)

This example explains well that reflexive+passive in Turkish  has its field of use. 

We also have verbs containing reflexive+passive combination:

aranıl(mak), yüklenil(mek),etc. 

..and an adjective: 

kaçınılmaz

Maybe there are a few more but these are what I remember at the moment.

The pleasure is all mine.

Reflexive + passive certainly has its function in language as your examples show, scalpel. But still it doesn´t erase the fact that there is always a chance for analogy also. We can say it is even probable that these forms spread wider than they were actually ment for by means of analogy, just like gokuyum said earlier. Because for an average language user it is a choice between models: real models and invented models, understood and misunderstood models...

Wow, this turned out a nice thread eventually (even though at some point I thought I messed it).

"There is always a chance for analogy also" .. Yes, there is and we can´t control it.. As you said "an average language user"  may be tempted to form new words by analogy.. I have a dictionary published in 60´s  and it says ´ya da´ is a badly made-up thing in place of ´veya´ and shouldn´t be used, and now in 2011 almost we all use ya da and veya is already an archaic word..  

Thank you Abla for supporting my idea. I think analogy is the main reason of this situation. Some people subconsciously think there is only one way to do passive and they use "n" as a buffer letter. I also want to thank scalpel too. Once upon a time he recommended me Feyza Hepçilingirler´s Turkish grammar book and I liked the book a lot and started to understand Turkish grammar better and think about it. 

The primary function of -n- is forming reflexive verbs often from transitives and reflexives are often intransitive: al-ı-n, sal-ı-n, gez-i-n, giy-i-n, dola-n, tıka-n, bul-u-n, aç-ı-n, öğre-n, tut-u-n, döv-ü-n, sakla-n, ara-n, taşı-n, sür-ü-n, söyle-n, kaç-ı-n, mırılda-n, tap-ı-n, etc. It is one of the most widely used suffixes from verb to verb.

The secondary function of -n- is forming passive verbs where the suffix -l- (which is the genuine suffix for passive) is not possible (verbs ending in a vowel or consonant -l)

ara-n (arandı belasını buldu), söyle-n (söylene söylene gitti), süsle-n (kadın süslendi), sil-i-n (silinip kurulandı ) are reflexive.

ara-n (ev arandı ), söyle-n (söz söylendi), süsle-n (şehir süslendi), sil-i-n (camlar silindi) are passive.

Either because of (as you said above) -n- is not considered as a passive suffix, or because to avoid confusion between the two uses, we can add -l- to -n-: başla-n-ı-l, de-n-i-l, ye-n-i-l, bul-u-n-u-l, oku-n-u-l,ara-n-ıl, söyle-n-i-l,etc.

But what made this thread turn into an interesting one is something else.. We shared our opinions about the "reflexive+passive" combination and its possible field of use..      

Average language users have surprisingly strong opinions about what is right and what is wrong and they are motivated to make right choices. The problem is that few people can really analyse the flow of language. I can imagine that the double role of -n- in derived Turkish verbs may be a reason for speakers to make further differentiations.

A good discussion is a rare thing. We people tend to take things personally and stick to our old views stubbornly. It concerns each one of us. When someone has typed half a page to make you understand a new thing the first reaction  -  to be honest  - is "what is he trying to prove, I know this better, who does he think he is". It is a protection mechanism which we need to get along but still a great obstacle to any learning.

Hmm. OK.

We can also make reflexive construction as in English.

Kendisini yıkadı = He washed himself.

In that case passive can not be used.

I wonder why. kendi can´t take the place of the subject or what?

Kendisi yıkandı.

Here "yıkandı" should be passive but concieved as reflexive.

Kendisi yıkandı = He washed himself by himself.

Aaa...like we got to the same point again.

I have visited the wikipedia page again:

In most languages that allow impersonal passives, only unergative verbs may undergo impersonal passivization.  Unaccusative verbs may not.  The ability to undergo this transformation is a frequently used test to distinguish unergative and unaccusative verbs.  In Turkish, for example, the verb çalışmak "to work" is unergative and may therefore be passivized:

Burada çalış-ıl-ır.

here work-PASS-PRESENT

"Here it is worked."

The verb ölmek "to die", however, is unaccusative and may not be passivized:

*Burada öl-ün-ür.

here die-PASS-PRESENT

"Here it is died."

However its conclusion about unacusative verbs is not the case in Turkish.

For example "burada ölünür" is meaningful in Turkish.

Burada ölünür = "here it is died" (literally not meaningful in English)

meaning this is the place one can die (directly) or

this is the place one should live until he dies (indirectly)

Similarly you can say:

Burada doğulur = This is the place to be born

Well done, si++. These things that you write about unaccusative verbs ölmek and doğmak I could translate straight into Finnish and it would be valid information. There is a (narrow) use for täällä kuol|la|an and täällä synny|tä|än. But using them in speech requires a good sense of style because they are not quite normal language.

Somehow the whole concept of ergativity has slipped my memory. I remember having studied it a couple of times for exams a long time ago but obviously I have forgotten it the next day. Maybe it´s time to brush up some things.