Etymology
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luff (n.)
also loof, in sailing, c. 1200, "contrivance for altering a ship's course," also "part of a ship's bow where the sides begin to curve," from Old French lof "spar," or some other nautical device, "point of sail," also "windward side," of uncertain origin and sense development, probably ultimately from Germanic (compare Middle Dutch lof "windward side of a ship" (Dutch loef), which might also be the direct source of the English word).

This is from Proto-Germanic *lofo (source also of Old Norse lofi, Gothic lofa "palm of the hand," Danish lab, Swedish labb "paw"), from PIE *lep- (2) "to be flat" (see glove (n.)). As a verb, "bring the head of a sailing-ship nearer the wind," from late 14c., from the noun.
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aloof (adv.)
1530s, "to windward," from a- (1) "on" + Middle English loof "windward direction," probably from Dutch loef (Middle Dutch lof) "the weather side of a ship" (see luff (n.)). Originally in nautical orders to keep the ship's head to the wind, thus to stay clear of a lee-shore or some other quarter; hence "at a distance but within view" (1530s) and, figuratively, "apart, withdrawn, without community spirit" (with verbs stand, keep, etc.). As an adjective from c. 1600. Related: Aloofly; aloofness.
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stroppy (adj.)

"rebellious," by 1943, British nautical slang, perhaps a slang mangling of obstreperous. "Sea Passages: A Naval Anthology and Introduction to the Study of English" [1943, Geoffrey Callender] quotes from a letter:

Why Nobby should reckon that his raggie should blow the gaff, when there are crushers everywhere, leaves me guessing; but there it is. In the last dog he rounded on me and called me a white rat. I got stroppy and told him he was shooting a line: but all he said was, 'Oh! choke your luff! I'm looking for another oppo you snivelling sand-catcher.' So that looks like paying off.

to which Callender adds, "There is nothing in this letter which an active service rating could fail to understand."

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