"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." It is thus related to Greek ostrakon "a hard shell" and to osteon "a 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 recorded from 1690s. Oysterman "man engaged in rearing, taking, or selling oysters" is attested from 1550s. The common statement that edible oysters are in season only in months that end in -r is recorded by 1765.