reef n.1

Old English ribb "a rib; one of a series of long, slender, curved bones of humans and animals, forming a kind of cage or partial enclosure for the chief organs," from Proto-Germanic *rebjan (source also of Old Norse rif, Old Saxon ribbi, Old Frisian rib, reb, Middle Dutch, Dutch ribbe, Old High German ribba, German Rippe).

Boutkan finds the old derivation of this from PIE *rebh- "to roof, cover" (on the notion of "a covering" of the cavity of the chest) doubtful, "particularly because the alleged semantic development to 'rib' is found only in Gmc. and Slavic."

Cookery sense of "piece of meat from an ox, pig, etc. containing one or more ribs" is from early 15c. As "a ship's curved frame timber" from 1550s.

Rib-roast "joint of meat for roasting which includes one or more ribs" is by 1889. Rib-eye for a cut of meat that lies along the outer side of a rib is by 1926, American English, with eye in a specialized sense in butchery. Rib joint "brothel" is slang from 1943, probably in reference to Adam's rib (compare rib "woman, wife," attested from 1580s).

general name for the hard, calcareous skeleton excreted by certain marine polyps, c. 1300, from Old French coral (12c., Modern French corail), from Latin corallium, from Greek korallion, a word perhaps of Semitic origin (compare Hebrew goral "small pebble," Arabic garal "small stone").

Originally especially the red variety found in the Mediterranean, used ornamentally, hence "red, the (red) color of coral" (mid-15c.). As an adjective, "made of coral," mid-15c. The coral-snake (1760) is so called for the red zones in its markings. Coral-reef is attested from 1745 (see reef (n.1)).

"marijuana cigarette," 1920s, perhaps an alteration of Mexican Spanish grifo "marijuana, drug addict" [OED]; or perhaps from reef (v.), on resemblance to a rolled sail. It also meant "pickpocket" in criminal slang (by 1935), and Century Dictionary also has it as "oyster that grows on reefs in the wild."

Reefer also was a nickname for the sailing navy's equivalent to a midshipman (1818) "because they attend in the tops during the operation of reefing" [Century Dictionary], which is the source of the meaning "coat of a nautical cut" (1878) worn by sailors and fishermen "but copied for general use in the fashions of 1888-90" [CD].