"room containing a sink," 1869, from sink (n.) + room (n.). In U.S. (New England) especially such a room adjoining a kitchen, hence "scullery."
Entries linking to sink-room
sink n.
early 15c., "cesspool, pit for reception of wastewater or sewage," from sink (v.). The meaning "drain for carrying water to a sink" is from late 15c., and the sense of "shallow basin (especially in a kitchen) with a drainpipe for carrying off dirty water" is by 1560s.
The figurative sense of "place where corruption and vice abound, abode or resort of depraved or debauched persons" is from 1520s. In science and technical use, "place where heat or other energy is removed from a system" (opposite of source), from 1855, from the notion of sink as "receptacle of waste matter."
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 Roomth "sufficient space" (1530s, with -th (2)) now is obsolete.