association (n.) Look up association at Dictionary.com
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" (see social (adj.)). 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.