"unsuitably, unseasonably," 1660s, from French mal à propos "inopportunely, inappropriately," literally "badly for the purpose," from mal (see mal-) + proposer "to propose, advance, suggest," from pro "forth" (see pro-) + poser "put, place" (see pose (v.1)). As an adjective, "inappropriate, out of place," by 1711.
