associative (adj.)

mid-15c., "join in company, combine intimately" (transitive), from Latin associatus past participle of associare "join with," from assimilated form of ad "to" (see ad-) + sociare "unite with," from socius "companion, ally" (from suffixed form of PIE root *sekw- (1) "to follow"). Related: Associated; associating.

The intransitive sense of "have intercourse, be associated" is from 1640s. The earlier form of the verb was associen (late 14c.), from Old French associier "associate (with)."

word-forming element making adjectives from verbs, meaning "pertaining to, tending to; doing, serving to do," in some cases from Old French -if, but usually directly from Latin adjectival suffix -ivus (source also of Italian and Spanish -ivo). In some words borrowed from French at an early date it has been reduced to -y (as in hasty, tardy).