1650s, "to fondle, caress, indulge, make a pet of," from a noun (1570s) meaning "lamb brought up as a pet" (applied to persons from 1590s), of uncertain origin. Perhaps [Skeat] from Old English cot-sæta "one who dwells in a cot" (see cote (n.) + sit (v.)). Related: Coseted; coseting. Compare German Hauslamm, Italian casiccio.
