Koss-ommak: two words , the first : koss means "Pussy" in most of the Arabic countries and or/accents.
The second : Ommak means your mom in all Arabic countries and/or accents.
In the Arabic countries : insulting the Religion and/or Mother is the maximum you can do when you need to offend someone , since most of the people share the same religion , it is the most widely used word to offend others.
Hey you ...Kossommak ! The Arabic equivelant of Mother Fucker ( yet it does not mean the same action but leads to the insult of the mother as well).
Kossomm Kida ( this ) : something like Fuck this !
Kossommeen : mother fucker to the infinity !