Where does “plъ̃tъ” come from?

plъ̃tъ (Proto-Slavic) comes from Proto-Indo-European plew- — to fly, flow, run.

Ancestry of “plъ̃tъ”, step by step

Step	Language	Word	Meaning
1	Proto-Indo-European	plew-	to fly, flow, run

plъ̃tъ — Etymology, Origin & Word History | Etymology Explorer