(covers information from several alternate timelines)
Oyster was the common name of a number of different groups of bivalve mollusks native to the planet Earth, most of which lived in marine habitats. The shell consisted of two usually highly calcified valves which surrounded a soft body. The oysters known as "true oysters" were highly prized as food, both raw and cooked.
In 1893, a young Jack London mentioned to Data that among his wide spectrum of previous occupations he used to be an oyster pirate. Samuel Clemens, who later inspired London to take up writing, joked that even oysters probably required fifteen million years to "come out just right" when discussing the relative age of the Earth to the existence of Humankind. (TNG: "Time's Arrow")
Fried oysters – stuffed oysters fried to tender perfection with a creamy green onion dipping sauce – were on the menu at Sisko's Creole Kitchen when Jake and Benjamin Sisko visited in 2372. (DS9: "Paradise Lost")
Oysters are the main ingredient in oysters Rockefeller, a rich Earth food made of a combination of oysters, spinach, parsley, and Parmesan cheese, topped with a rich white sauce of butter, flour, and milk. On their first date, Odo and Kira Nerys had oysters Rockefeller with a '55 Dom Pérignon. (DS9: "His Way")