Where does “*āpē-” come from?

*āpē- (Proto-Baltic) comes from Proto-Indo-European h₂ep- — water, body of water.

Ancestry of “*āpē-”, step by step

Step	Language	Word	Meaning
1	Proto-Indo-European	h₂ep-	water, body of water

*āpē- — Etymology, Origin & Word History | Etymology Explorer