Middle English word abetten comes from Old French a-, Old French beter

Detailed word origin of abetten

Dictionary entry	Language	Definition
a-	Old French (fro)	(by extension) indicating a change of state. Indicating movement towards something. Intensifying prefix.
beter	Old French (fro)
abeter	Old French (fro)
abette	Middle English (enm)

Words with the same origin as abetten