deficient (adj.)

1580s, "lacking, wanting, incomplete;" c. 1600 "not having a full or adequate supply," from Latin deficientem (nominative deficiens), present participle of deficere "to desert, revolt, fail," from de "down, away" (see de-) + combining form of facere "to do, make" (from PIE root *dhe- "to set, put"). Compare defective. Related: Deficiently.