early 15c., "to convey (truth) in a fable," from Latin implicatus, past participle of implicare "to involve, entwine, entangle, embrace," from assimilated form of in- "into, in, on, upon" (from PIE root *en "in") + plicare "to fold" (from PIE root *plek- "to plait"). From c. 1600 as "intertwine, wreathe." Meaning "involve (someone) in a crime, charge, etc.; show (someone) to be involved" is from 1797. Related: Implicated; implicating.
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).