What does it mean? Where does it come from?

I believe it´s the equivalent of Romeo and Juliet in Turkish culture.

https://en.wikipedia.org/wiki/Layla_and_Majnun

it is true but Mecnun kicks Romeo´s ass

Yeah, I bet he makes Romeo look like a pussycat, with all his poetry and crying in the desert and what not  

So, this doesn´t have anything to do with being drunk? I thought Leyla meant something like that. I´m probably wrong. Just checking.

Yes it means "distracted", "miles away" or "drunk". And these metaphors have their roots in the story. (like being drunkened or blinded by love)