"something stored up," 1610s, from reserve (v.) or from French réserve, a Middle French back-formation from reserver "set aside, withhold," from Latin reservare "keep back, save up; retain, preserve," from re- "back" (see re-) + servare "to keep, save, preserve, protect" (from PIE root *ser- (1) "to protect"). Meaning "self-imposed restraint on freedom of words or actions; habit of keeping back the feelings" is from 1650s.
