Where does “کار” come from?

کار (Classical Persian) comes from Middle Persian kʾl, from Proto-Indo-European kʷer- — to do; to make; to build.

Ancestry of “کار”, step by step

Step	Language	Word	Meaning
1	Middle Persian	kʾl	work, deed, affair
2	Proto-Indo-European	kʷer-	to do; to make; to build