CASKET, a small box or coffer, commonly used for jewels, money, papers, or other objects of value. The etymology is doubtful. It is possibly a diminutive of "cask," a barrel for wine or other liquor. The Spanish casco meant also a skull, helmet, or rind of an onion, and is probably connected with cascar, to break open, Latin quassare, French casser, to break, shake. The French casque, casquet, of the same origin is only used of a helmet, and the sense of "small chest" is not found in languages other than English. Skeat suggests that the word is a corruption of French cassette, diminutive of casse, box, Latin capsa, from capere, to hold, contain, cf. English "case." History and literature are full of references to the often disconcerting contents of these famous receptacles. The "Casket Letters" (q.v.) are one of the mysteries of history. Harpagnon's casket plays an important part in Molière's L'Avare; Bluebeard gives his too-curious wife the keys of his caskets filled with precious stones; the contents of Sainte-Croix's casket brought about the trial and condemnation of the marquise de Brinvilliers, the poisoner. This very ancient piece of furniture was no doubt derived from the chest, which was the original wardrobe. It was often an object of great value, covered with ivory, enamel, or stamped leather, enriched with precious metals, or encrusted with jewels. One which belonged to St Louis and is preserved in the Louvre is covered with enamelled shields of arms and other decorations. In the 16th and 17th centuries secret hiding-places were sometimes in the thickness of the lid or in a false bottom. The word is now little used - the natural result of the desuetude of the object; but auctioneers occasionally announce that they will sell a "casket of jewels," and undertakers, especially in the United States, frequently use it as a grandiose synonym for "coffin."
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)