Where does “cōs” come from?

cōs (Latin) comes from Ancient Greek Κῶς, from Hebrew כוס, from Arabic كُسّ.

Ancestry of “cōs”, step by step

Step	Language	Word	Meaning
1	Ancient Greek	Κῶς	—
2	Hebrew	כוס	A cup, glass, tumbler; little owl; A pussy
3	Arabic	كُسّ	—