penguin

Etymology

Unknown; first attested in the 16th century in reference to the auk of the Northern hemisphere; the word was later applied to the superficially similar birds of the Southern hemisphere (as was woggin). Possibly from Welsh pen (“head”) and gwyn (“white”), or from Latin pinguis (“fat”). See citations and the Wikipedia page. (nun): Because of the often black-and-white habit, resembling the bird's colors.

noun

1. Any of several flightless sea birds, of order Sphenisciformes, found in the Southern Hemisphere, marked by their usual upright stance, walking on short legs, and (generally) their stark black and white plumage.
   Here are also birds cal'd Pen-gwins (white-head in Welch) like Pigmies walking upright, their finns or wings hanging very orderly downe like sleeves […] 1638, Thomas Herbert, Some Yeares Travels, section I
2. (obsolete or historical) An auk (sometimes especially a great auk), a bird of the Northern Hemisphere.
   This last species of penguin, or auk, seems to be the same with the alca cirrhata of Dr. Pallis, Spicileg. Zool. Fasc. v. p. 7. tab. i. & v. fig. 1–3. F. 1772 March, “Account of the Settlement of the Malouines”, in The Gentleman's and London Magazine, page 166
   More than a hundred years ago, for example, was seen the last of the great wingless penguins or auks, which early writers quaintly called " wobble-birds." 1885, Journal of the American Geographical Society of New York
3. (slang) A nun.
4. (juggling) A type of catch where the palm of the hand is facing towards the leg with the arm stretched downward, resembling the flipper of a penguin.
5. A spiny bromeliad with egg-shaped fleshy fruit, Bromelia pinguin.
   These productive patches, and the houses, were each surrounded by a fence, made of a prickly shrub, called the Pinguin, which propagates itself with great rapidity. 1803, Robert Charles Dallas, The History of the Maroons, London: Longman and Rees, Volume 1, Letter 4, p. 82
6. (UK, military, slang) A member of the air force who does not fly aircraft.
   Although it is a permanent R.A.F. station (pre-war, that is), we meander about, even in the Mess, in battle dress and flying boots, sweaters, etc., much to the disgust of some of the more dignified 'penguins' […] 1942, Hermann Hagedorn, Sunward I've Climbed, page 143
   Notwithstanding his elevated status as the wing’s Senior Intelligence Officer, Monty, too, was a “penguin,” equal in that respect to an armament assistant, airframe mechanic, pigeon loftsman or any of the seventy-odd ground trades listed by the Royal Canadian Air Force at the war’s end. 1994, Monty Berger, Invasions without tears: the story of Canada's top-scoring Spitfire wing in Europe during the Second World War, →LCCN, page xi
   She may have been a “penguin”—an Air Force service member who didn't fly—but it sure beat being at home, as Brady had pointed out. 2015-06-01, Kate Christie, In the Company of Women, Bella Books, →OCLC
   This was to be my home for three months where ground officer cadets, referred to colloquially as ‘penguins’ were trained. 2019-11-05, Derek Esp, An Adventure in Education: The Autobiography of an Accidental Career in Education, Troubador Publishing Ltd, →OCLC, page 46