proficient (adj.)

1580s, back-formation from proficiency or else from Old French proficient (15c.), from Latin proficientem (nominative proficiens), present participle of proficere "to make progress, go forward, effect, accomplish, be useful," from pro "forward" (see pro-) + combining form of facere "to make, do" (from PIE root *dhe- "to set, put"). Related: Proficiently.