late 15c., "one who or that which multiplies or increases in number," agent noun from multiply. In arithmetic, "the number by which another is multiplied," 1540s.
mid-12c., multeplien, "to cause to become many, cause to increase in number or quantity," from Old French multiplier, mouteplier (12c.) "increase, get bigger; flourish; breed; extend, enrich," from Latin multiplicare "to increase," from multiplex (genitive multiplicis) "having many folds, many times as great in number," from combining form of multus"much, many" (see multi-) + -plex "-fold," from PIE root *plek- "to plait."
Intransitive sense of "grow or increase in number or extent" (especially "to have children, produce offspring") is from mid-14c. Mathematical sense "perform the process of multiplication" is attested from late 14c. Related: Multiplied; multiplying.
Greek god of shepherds and flocks, woods and fields, with upper body of a man and horns and lower part like a goat, late 14c., from Latin, from Greek Pan. Klein and others suggest the Greek word is cognate with Sanskrit pusan, a Vedic god, guardian and multiplier of cattle and other human possessions, literally "nourisher," from a PIE root *peh- "to protect," but others doubt this.
His worship originated in Arcadia and gradually spread throughout Greece. The similarity to pan "all" (see pan-) led to his being regarded as a general personification of nature. He was fond of music and dancing with the forest nymphs; the pan-pipe, which he invented and upon which he played, is attested by that name in English from 1820.