Middle English word an- comes from Old English on-

Detailed word origin of an-

Dictionary entry	Language	Definition
on-	Old English (ang)	Denoting reverse action. Off, away (inchoactive) in, into; prefix used to intensify an action or to denote origin or initiation. Forming verbs and adjectives from participles and nouns, with various senses of on, upon, to, there, thither.
and-	Middle English (enm)

Words with the same origin as an-