1540s, "flesh or meat of the belly" (a sense now obsolete), from Latin abdomen "the belly," a word of unknown origin, Perhaps [OED, Watkins] from abdere "conceal" (from ab "off, away" + PIE root *dhe- "to set, put"), with a sense of "concealment of the viscera," or else "what is concealed" by proper dress. De Vaan, however, finds this derivation "unfounded." Anatomical sense "part of the mammalian body between the diaphragm and the pelvis" is from 1610s. Zoological sense of "posterior division of the bodies of arthropods" by 1725.
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.
"animals of the mammalian order Cetacea," Old English hwæl "whale," also "walrus," from Proto-Germanic *hwalaz (source also of Old Saxon hwal, Old Norse hvalr, hvalfiskr, Swedish val, Middle Dutch wal, walvisc, Dutch walvis, Old High German wal, German Wal), from PIE *(s)kwal-o- (source also of Latin squalus "a kind of large sea fish"). In popular use it was applied to any large sea animal. Phrase whale of a "excellent or large example" is c. 1900, student slang. Whale-oil attested from mid-15c.