Where does “plāntā” come from?

plāntā (Proto-Italic) comes from Proto-Indo-European pléh₂-n̥t-eh₂, from Proto-Indo-European pleh₂- — flat.

Ancestry of “plāntā”, step by step

Step	Language	Word	Meaning
1	Proto-Indo-European	pléh₂-n̥t-eh₂	—
2	Proto-Indo-European	pleh₂-	flat

plāntā — Etymology, Origin & Word History | Etymology Explorer