Where does “hapja” come from?

hapja (Frankish) comes from Proto-Germanic hapjō, from Proto-Indo-European kop- — to dig; to strike, to beat.

Ancestry of “hapja”, step by step

Step	Language	Word	Meaning
1	Proto-Germanic	hapjō	—
2	Proto-Indo-European	kop-	to dig; to strike, to beat

hapja — Etymology, Origin & Word History | Etymology Explorer