mid-15c., "set in order or readiness for a particular end," a back formation from preparation and in part from Old French preparer (14c.), from Latin praeparare "to make ready beforehand," from prae "before" (see pre-) + parare "to make ready" (from PIE root *pere- (1) "to produce, procure"). Compare pare (v.), which is from the same Latin verb. Related: Prepared; preparer; preparing.
Intransitive sense of "make (oneself) ready beforehand" is from c. 1500. The sense of "bring into a particular mental state with reference to the future" is by 1520s. The sense of "make (food) ready to eat" is from late 15c. (Caxton). The meaning "provide or procure for future use" is from 1530s. An earlier verb was preparate (late 14c.), from Latin praeparatus, past participle of praeparare. The Boy Scouts' motto Be Prepared is attested from 1911, based, as he said, on the initials of the organization's founder, Robert Baden-Powell.