Old English rum "space" (extent or time); "scope, opportunity," 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."
The original sense is preserved in make room "clear space for oneself" (late 14c.). The meaning "chamber, cabin" is recorded by early 14c. as a nautical term, and applied by mid-15c. to chambers within houses; the Old English word for this was cofa, ancestor of cove.
Room-service is attested from 1913; room-temperature from 1879. Roomth "sufficient space" (1530s, with -th (2)) now is obsolete.
"to occupy rooms" (especially with another) as a lodger," 1828, from room (n.). Related: Roomed; rooming. Rooming-house is from 1889. In Old English (rumian) and Middle English the verb meant "become clear of obstacles; make clear of, evict."