Where does “a-” come from?

a- (Old Spanish) comes from Latin ad-, from Latin īn-, from Latin în, from Latin en, from Proto-Italic en, from Proto-Indo-European h₁én — in.

Ancestry of “a-”, step by step

StepLanguageWordMeaning
1Latinad-to; usually prefixed to verbs, in which cases it...
2Latinīn-un-, non-, not
3Latinînin, at, on, upon, from (space)
4Latinenlookǃ beholdǃ; reallyǃ?; come onǃ
5Proto-Italicenin
6Proto-Indo-Europeanh₁énin

Words derived from “a-”

Every word from Proto-Indo-European h₁én →Every word from Latin īn- →Every word from Latin ad- →