"member of a community or fraternity of men formed for the practice of religious devotions or duties and bound by certain vows," Old English munuc (used also of women), from Proto-Germanic *muniko- (source also of Old Frisian munek, Middle Dutch monic, Old High German munih, German Mönch), an early borrowing from Vulgar Latin *monicus (source of French moine, Spanish monje, Italian monaco), from Late Latin monachus "monk," originally "religious hermit," from Ecclesiastical Greek monakhos "monk," noun use of a classical Greek adjective meaning "solitary," from monos "alone" (from PIE root *men- (4) "small, isolated"). The original monks in Church history were men who retired from the world for religious meditation and the practice of religious duties in solitude. For substitution of -o- for -u-, see come.
In England, before the Reformation, the term was not applied to the members of the mendicant orders, who were always called friars. From the 16th c. to the 19th c., however, it was usual to speak of the friars as a class of monks. In recent times the distinction between the terms has been carefully observed by well-informed writers. In French and Ger. the equivalent of monk is applied equally to 'monks' and 'friars.' [OED]
for historical evolution, see V. Used punningly for you by 1588 ["Love's Labour's Lost," V.i.60], not long after the pronunciation shift that made the vowel a homonym of the pronoun. As a simple shorthand (without intentional word-play), it is recorded from 1862. Common in business abbreviations since 1923 (such as U-Haul, attested from 1951).
The substitution of Middle English -o- for Old English -u- before -m-, -n-, or -r- was a French scribal habit before minims to avoid misreading the letters in the old style handwriting, which jammed them together. The practice transformed some, come, monk, tongue, worm.
Bavarian capital, German München, from root of Mönch "monk" (see monk); founded 1158 as a market town by Benedictine monks. In allusions to "appeasement" it is from the meeting of German, British, French and Italian representatives there on Sept. 29, 1938, which resulted in the cession of Sudetenland to Germany in exchange for Hitler's pledges.
During the flight [from Munich] Daladier sat silent and morose, worried about the reception he would receive at Le Bourget, about how the French would react to his having betrayed Czechoslovakia and France's promises. As the plane circled for landing, he and others saw a massive crowd awaiting them. Expecting jeers, hisses, rotten fruit, and maybe worse, Daladier declared stolidly: 'They are going to mob me, I suppose. ... I appreciate their feelings,' and insisted on absorbing their wrath by being the first off the plane. But as he stood dumbfounded on the gangplank, thousands surged forward carrying flags and flowers, shouting 'Hurrah for France! Hurrah for England! Hurrah for peace!' Daladier turned back to Léger and cursed, 'The God-damned fools!' [Benjamin F. Martin, "France in 1938"]
figurative for a puritan attitude toward the arts at least since Shaw (1916), from the name of Girolamo Savonarola (1452-1498), Dominican monk famous for his fierce opposition to moral licence and Church corruption.
c. 1600, "pertaining to the Cistercian order of monks," with -an + Medieval Latin Cistercium (French Cîteaux), near Dijon, site of an abbey where the monastic order was founded 1098 by Robert of Molesme. As a noun, "monk of the Cistercian order," from 1610s.
"a nun, a religious woman," 1690s, from French religieuse, fem. of religieux "monk, religious person" (itself used in English from 1650s but much less common), noun use of the adjective meaning "religious" (see religious). As a type of pastry, attested from 1929.