1530s, nyppell, "protuberance of a mammalian breast," in a female the extremity where the milk-ducts discharge, alteration of neble (1520s), probably diminutive of neb "bill, beak, snout" (see neb), hence, literally "a small projection." Used from 1713 of any thing or mechanical part that projects like a nipple. From 1875 in reference to the mouthpiece of an infant's nursing-bottle. Earlier words were pap (n.2), teat. A 16c.-17c. slang term for a woman's nipples was cherrilets.
plural papillae, 1690s, "a nipple of a mammary gland," from Latin papilla "nipple," diminutive of papula "swelling" (see pap (n.2)). Meaning "nipple-like protuberance" attested from 1713.
"animal nipple," or, contemptuously, "the human female breast," originally with reference to suckling, 1520s, origin obscure, perhaps related to Swedish dagga, Danish dægge "to suckle."
"nipple of a woman's breast," late 12c., pappe, first attested in Northern and Midlands writing, probably from a Scandinavian source (not recorded in Old Norse, but compare dialectal Swedish pappe), from PIE imitative root *pap- "to swell" (source also of Latin papilla "nipple," which might rather be the source of the English word, papula "a swelling, pimple;" Lithuanian papas "nipple"). Like pap (n.1) supposed to be ultimately of infantile origin.
1530s, "one who pacifies or appeases," agent noun from pacify. The meaning "nipple-shaped device for babies" is recorded by 1904. Pacificator "a peacemaker" (1530s) is directly from Latin.