"bag-like case of cloth, etc., stuffed with soft material and used as a support or for comfort for some part of the body," c. 1300, quishin, from Anglo-French quissyn, Old French coissin "seat cushion" (12c., Modern French coussin), cognate with Medieval Latin cossinus, probably a variant of Vulgar Latin *coxinum, from Latin coxa "hip, thigh," or from Latin culcita "mattress." Someone has counted more than 400 spellings of the plural of this word in Middle English wills and inventories, including quessihon, quoshin, whishin, cuishun, kuchin, koshen. Also from the French word are Italian cuscino, Spanish cojin. Figurative sense of "something to absorb a jolt, shock, etc." is by 1860.
1730s, "to seat on or as on a cushion," from cushion (n.). From 1820 as "furnish with a cushion or cushions." In the figurative sense, "mitigate or absorb the impact of something," by 1863. Related: Cushioned; cushioning.