Where does “akki” come from?

akki (Proto-Celtic) comes from Proto-Indo-European peh₂ḱ- — to join, to attach; agreement, settlement.

Ancestry of “akki”, step by step

Step	Language	Word	Meaning
1	Proto-Indo-European	peh₂ḱ-	to join, to attach; agreement, settlement

akki — Etymology, Origin & Word History | Etymology Explorer