Meaning

noun a person who joins with others in some activity or endeavor

noun a friend who is frequently in the company of another

noun a person with subordinate membership in a society, institution, or commercial enterprise

originFrom Middle English associat(e) (used participially as well as adjectively up to Early Modern English), from Latin associātus, the perfect passive participle of associō (“to join, unite”), from ad- + sociō, from socius (“shared, common, kindred”) + -ō (first conjugation verb-forming suffix).

Etymology from Wiktionary, CC BY-SA 3.0