Association
mid 16th century (in the sense ‘uniting in a common purpose’): from medieval Latin associatio(n- ), from Latin associare ‘to unite, ally’ (see associate).
wiktionary
From Latin associātiō, from associō (perhaps via French association). Morphologically associate + -ion
etymonline
association (n.)
1530s, "action of coming together for a common purpose," from Medieval Latin associationem (nominative associatio), noun of action from past-participle stem of associare "join with," from assimilated form of ad "to" (see ad-) + sociare "unite with," from socius "companion, ally" (from PIE *sokw-yo-, suffixed form of root *sekw- (1) "to follow"). Meaning "an organized body of persons with a common purpose" is from 1650s. Meaning "mental connection" is from 1680s; that of "quality or thing called to mind by something else" is from 1810.
