Nere-den

den is from.

Nereden means from where

thank you and now is it still it or he/she

It depends on context. But I think it is it. Translation is sometimes like solving a puzzle. 

 Agree, a short sentence (often from a text, or Facebook) needs to be in context.

I would think it is the same as "No. Where did that come from now?" or "No. Where did you get that idea from?" in English.

You can´t translate literally when dealing with colloquial expressions. O nereden çıktı means literally "where did he/she/it appear from". But it is usually used as "where did it come from". If said in response to a surprising comment (as implied by the "yok"), it is more likely "where did that idea come from".