cushionyoudaoicibaDictYouDict[cushion 词源字典]
cushion: [14] Ultimately, cushion and quilt are the same word. Both come from Latin culcita ‘mattress, cushion’, which is related to Sanskrit kūrcás ‘bundle’, and both reached English via rather circuitous routes. In Gallo-Roman (the descendant of Latin spoken in France from the 5th to the 9th centuries) culcita underwent a transformation which produced Old French coissin and cussin, which Middle English borrowed as quisshon and cushin.

The complexity of forms spawned by these was quite staggering – the OED records nearly seventy spellings of the word – but by the 17th century things had settled down, with cushion emerging the winner. Cushy [20], incidentally, is quite unrelated, being a borrowing from Hindi khūsh ‘pleasant’.
=> quilt[cushion etymology, cushion origin, 英语词源]
cushion (n.)youdaoicibaDictYouDict
c. 1300, from Old French coissin "seat cushion" (12c., Modern French coussin), 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. Also from the French word are Italian cuscino, Spanish cojin.
cushion (v.)youdaoicibaDictYouDict
1730s, from cushion (n.). In the figurative sense, from 1863. Related: Cushioned; cushioning.