mid-15c., from Latin associatus past participle of associare "join with," from ad- "to" (see ad-) + sociare "unite with," from socius "companion" (see social, adj.). Related: Associated; associating. Earlier form of the verb was associen (late 14c.), from Old French associier "associate (with)."

1530s, from associate, adj..

early 15c., "allied, connected, paired," from Latin associatus, past participle of associare (see associate, v.).