c. 1300, "to spread or lay on a surface, to overlay," from Old French couchier "to lay down, place; go to bed, put to bed," from Latin collocare "to lay, place, station, arrange," from assimilated form of com "with, together" (see com-) + locare "to place," from locus "a place" (see locus).
From late 14c. as "to lie down" (intransitive), also "cause to recline upon a bed or other resting place" (transitive). Meaning "lie hidden" is from 1580s. From 1520s as "to put into words;" hence "include the meaning of a word or statement, express in an obscure or veiled way, imply without distinctly saying" (1560s). Related: Couched; couching.
Heraldic couchant ("lying down with the head up") is late 15c., from the French present participle.
mid-14c., "a bed," from Old French couche "a bed, lair" (12c.), from coucher "to lie down," from Latin collocare (see couch (v.)). From mid-15c. as "a long seat upon which one rests at full length." Traditionally, a couch has the head end only raised, and only half a back; a sofa has both ends raised and a full back; a settee is like a sofa but may be without arms; an ottoman has neither back nor arms, nor has a divan, the distinctive feature of which is that it goes against a wall.
As symbolic of a psychiatric treatment or psychoanalysis, by 1952. Couch potato first recorded 1979.
in couch-grass, 1570s; a corruption of Old English cwice "living, alive" (see quick (adj.)).