According to كيس - Wiktionary seems that it's borrowed from Akkadian to Aramaic to Arabic. They provide no further info.How do we know كيس is a borrowing and not a cognate?
But, Are we considered "sex" word indicate to Persian word "kus" ??They are not related. كيس (kīs | bag) and كس (kuss, kiss | vagina). The first one is from Aramaic and found in Hebrew, Syriac and Akkadian as well. The latter is borrowed from Persian كس (kos), from proto-Indo-European.
Probably an Iranian borrowing, but the details are uncertain. Likely from the family of Persian کس (kos, “pussy”). Alternatively, from the family of Classical Persian کوسه (kōsa, “man with little or no beard”).Is kus related with Armenian կոյս guys (virgin girl)?