late 14c., "outcome of an action," from Old French esploit "a carrying out; achievement, result; gain, advantage" (12c., Modern French exploit), a very common word, used in senses of "action, deed, profit, achievement," from Latin explicitum "a thing settled, ended, or displayed," noun use of neuter of explicitus, past participle of explicare "unfold, unroll, disentangle," from ex "out" (see ex-) + plicare "to fold" (from PIE root *plek- "to plait").
Meaning "feat, achievement" is c. 1400. Sense evolution is from "unfolding" to "bringing out" to "having advantage" to "achievement." Related: Exploits.
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).