Where does “*baþjaną” come from?

*baþjaną (Proto-Germanic) comes from Proto-Indo-European bʰeh₁- — to foment; warm; bathe.

Ancestry of “*baþjaną”, step by step

Step	Language	Word	Meaning
1	Proto-Indo-European	bʰeh₁-	to foment; warm; bathe

*baþjaną — Etymology, Origin & Word History | Etymology Explorer