It's persian (farsi) for Pimp but it has taken another tone in a common vocabulary. It can be used to replace fucker,
asshole,
buddy, bro. It all depends of how you use it. It can be a friendly word or a very nasty
one depending to the way it is used. It's as powerful as the word fucker.
example
1 :
hey koskesh, you were supposed to call me
what happened?
example 2:
that koskesh
will get what he deserves
example 3:
Don't do business with that koskesh, he would sell his own mom for a buck