The Etymology of Couch
Couch entered English around 1300 from Old French couche, a bed or place of repose. The Old French noun and verb both descend from coucher (to lay down) and ultimately from Latin collocare, "to place together" — the same root that gives modern English locate, location, locus, and collocation. For centuries the English word kept its bed-and-lair meanings: medieval romances speak of knights couching their lances (laying them down level), and a hunted deer’s couch was its hidden resting-place. Only in the early modern period did couch begin to specialise toward the upholstered indoor furniture sense, gradually overlapping with sofa (a Turkish loanword) and settee. The verb survives in two register-distant senses: technically (to lower a lance, a sail, an animal) and figuratively (to couch criticism in polite language, where the metaphor is of laying words carefully into a sentence). Sofa eventually overtook couch in British use; American English kept couch as the everyday word.