mid-15c., malefactour, "a law-breaker, a criminal, a felon," from Latin malefactor, agent noun from past participle stem of malefacere "to do evil," from male "badly" (see mal-) + facere "to do, make" (from PIE root *dhe- "to set, put"). From late 15c. in the now-obsolete sense of "one who does evil or injury to another" (the opposite of benefactor).
It forms all or part of: beatific; beatify; beatitude; Beatrice; beau; beauty; Bella; belle; beldam; belladonna; belvedere; bene-; benedict; Benedictine; benediction; benefactor; beneficiary; benefice; beneficence; benefit; benevolent; benign; bonanza; bonbon; bonhomie; bonito; bonjour; bonny; bonus; boon (adj.); bounty; debonair; embellish.
It is the hypothetical source of/evidence for its existence is provided by: Latin bene (adv.) "well, in the right way, honorably, properly," bonus "good," bellus "handsome, fine, pretty," and possibly beatus "blessed," beare "to make blessed."