Other forms: caskets
A casket is a small ornamental box for jewels or valuables. A silver casket, a casket of letters, the jewel casket.
That is the older sense and the one in fairy tales and museums. In American English a casket is also a coffin, and it is now the usual funeral word there; British English keeps coffin for that and casket for the box. The two shapes differ as well: a coffin is wider at the shoulders and a casket is rectangular. Note that the American use began as an undertakers' euphemism in the nineteenth century.
1nouncasketA small ornamental box for jewels or valuables.
“The casket held nine letters and a ring.”
2nouncoffinA coffin.
“The casket was carried out by six of his grandchildren.”
casket is a box.
Norman cassette meant a little case, a diminutive of case. The same word came into English again much later as cassette, the tape, so a jewel box and a music tape are the same object named twice.
Norman
cassette
English, today
casket
Probably from Norman cassette. Possibly reformed by analogy with cask, thus analyzable as cask + -et. a doublet of cassette.
Etymology from Wiktionary, CC BY-SA