reefer (n.)

"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].

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