a call for silence and attention; the introduction to a proclamation made by an officer of a law-court," early 15c., from Anglo-French oyez "hear ye!" (late 13c., Old French oiez), a cry uttered (usually thrice) to call attention, from Latin subjunctive audiatis, plural imperative of audire "to hear" (from PIE root *au- "to perceive").

"edible bivalve mollusk of the family Ostreidæ," late 13c., oistre, from Old French oistre, uistre (Modern French huître) and directly from Latin ostrea, plural or fem. of ostreum "oyster," from Greek ostreon, from PIE root *ost- "bone." Related to Greek ostrakon "hard shell" and to osteon "bone." The h- in the modern French word is a regular development; compare huile "oil" (Latin oleum), huit "eight" (Latin octo).

Why then the world's mine Oyster, which I, with sword will open. [Shakespeare, "The Merry Wives of Windsor," II.ii.2]

Oyster-bed "place where oysters breed or are bred" is from c. 1600; oyster-knife, used for opening oysters, is from 1690s. Oysterman "man engaged in rearing, taking, or selling oysters" is from 1550s.

modified form of oxygen, 1840, from German Ozon, coined in 1840 by German chemist Christian Friedrich Schönbein (1799-1868) from Greek ozon, neuter present participle of ozein "to smell" (see odor). So called for its pungent odor. Related: Ozonic.