"water-tight, barrel-like vessel for containing liquids," mid-15c., from French casque "a cask; a helmet," from Spanish casco "skull; wine-vat; helmet," originally "potsherd," from cascar "to break up," from Vulgar Latin *quassicare, frequentative of Latin quassare "to shake, shatter" (see quash). The sense evolution is uncertain.
mid-15c., "small box for jewels, etc.," possibly a diminutive of English cask with -et, or from a corruption of French casset "a casket, a chest" (see cassette). Also a publisher's name for a collection of selected literary or musical pieces (1828). Meaning "coffin" (especially an expensive one) is American English, probably euphemistic, attested by 1832.
Thank Heaven, the old man did not call them "CASKETS!"—a vile modern phrase, which compels a person of sense and good taste to shrink more disgustfully than ever before from the idea of being buried at all. [Hawthorne, "Our Old Home," 1862]
"small cage for poultry," mid-14c., coupe, from Old English cype, cypa "large wicker basket, cask," akin to Middle Dutch kupe, Swedish kupa, and all probably from Latin cupa "tub, cask," from PIE *keup- "hollow mound" (see cup (n.)).
early 14c., "type of cask, large storage container;" mid-14c., "large vessel for storing wine," from Old French pipe "liquid measure, cask for wine," from a special use of Vulgar Latin *pipa "a pipe" (see pipe (n.1)).
"small cup-shaped depression or object," 1830, from Modern Latin cupula, diminutive of Latin cupa "cask, barrel" (see cup (n.)).