Etymology
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dining (n.)

c. 1400, "feasting, a feast," verbal noun from dine (v.). Dining-room "room in which principal meals are eaten" is attested from c. 1600. The railroad dining-car is from 1838.

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room (n.)

Middle English roum, from Old English rum "space, extent; sufficient space, fit occasion (to do something)," from Proto-Germanic *ruman (source also of Old Norse, Old Saxon, Old High German, Gothic rum, German Raum "space," Dutch ruim "hold of a ship, nave"), nouns formed from Germanic adjective *ruma- "roomy, spacious," from PIE root *reue- (1) "to open; space" (source also of Avestan ravah- "space," Latin rus "open country," Old Irish roi, roe "plain field," Old Church Slavonic ravinu "level," Russian ravnina "a plain").

Old English also had a frequent adjective rum "roomy, wide, long, spacious," also an adverb, rumlice "bigly, corpulently" (Middle English roumli).

The meaning "chamber, cabin" is recorded by early 14c. as a nautical term; applied by mid-15c. to interior division of a building separated by walls or partitions; the Old English word for this was cofa, ancestor of cove. The sense of "persons assembled in a room" is by 1712.

Make room "open a passage, make way" is from mid-15c.  Room-service is attested from 1913; room-temperature, comfortable for the occupants of a room, is so called from 1879. Roomth "sufficient space" (1530s, with -th (2)) now is obsolete.

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room (v.)

"to occupy a room or rooms" (especially with another) as a lodger," by 1825 (implied in roomed), from room (n.). Related: Rooming. Rooming-house, "house which lets furnished apartments," is by 1889, according to OED "chiefly U.S." In Old English (rumian) and Middle English the verb meant "become clear of obstacles; make clear of, evict."

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guest-room (n.)
also guestroom, 1630s, from guest (n.) + room (n.). Guest chamber is recorded from 1520s. Old English had giestærn "guest-chamber," with the second element the same one as in barn.
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living room (n.)
"room set up for ordinary family or social use, sitting-room," 1795 (as opposed to bedroom, dining room, etc.); from living (n.) + room (n.).
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leg-room (n.)
also legroom, 1846 (in reference to carriages), from leg (n.) + room (n.).
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ante-room (n.)
also anteroom, "small room giving access to a larger," especially a waiting room for visitors, 1762, literally "a room in front;" after French antichambre, Italian anticamera, from Latin ante "before" (see ante-) + camera (see chamber (n.)).
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bar-room (n.)
also barroom, "room in a tavern, etc., with a bar or counter where alcoholic drinks are served," 1797, from bar (n.2) + room (n.).
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drawing room (n.)

"room appropriated for the reception of company," 1640s, short for withdrawing room (16c.; see withdraw), into which ladies would retire after dinner. Earlier in the sense of "private room" as draw-chamber (mid-15c.); drawyng chaumber (early 15c.).

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