acquainted (adj.)

early 13c., "personally known;" past-participle adjective from acquaint (v.). Of skills, situations, etc., from late 15c.

I have been one acquainted with the night.

I have walked out in rain — and back in rain.

I have outwalked the furthest city light.

[Robert Frost, from "Acquainted with the Night"]

Acquaint also was used as an adjective (late 13c.) "acquainted."