"pertaining to the cavity of the abdomen," 1660s, from Latin coeliacus, from Greek koiliakos "pertaining to the bowels," also "pain in the bowels," from koilia "bowels, abdominal cavity, intestines, tripe" from koilos "hollow," from PIE root *keue- "to swell," also "vault, hole."
"white crystalline alkaloid present in opium," 1838, codeina, from French codéine, coined, with chemical suffix -ine (2), from Greek kodeia "poppy head," related to koos "prison," literally "hollow place;" kodon "bell, mouth of a trumpet;" koilos "hollow, hollowed out, spacious, deep," all from PIE root *keue- "to swell," also "vault, hole." Modern form is from 1881.
"having a body cavity distinct from the intestinal cavity," 1883, from Coelomata (1877), from Modern Latin neuter plural of coelomatus, from Greek koilomat- "hollow, cavity," from koilos "hollow, hollowed out, spacious, deep," from PIE root *keue- "to swell," also "vault, hole."
late 14c., "profound depth," from Old French golf "a gulf, whirlpool," from Italian golfo "a gulf, a bay," from Late Latin colfos, from Greek kolpos "bay, gulf of the sea," earlier "trough between waves, fold of a loose garment," originally "bosom," the common notion being "curved shape." This is from PIE *kuolp- "arch, curve, vault" (compare Old English hwealf"vault," a-hwielfan "to overwhelm," Old Norse holfinn "vaulted," Old High German welban "to vault").
Latin sinus underwent the same development, being used first for "bosom," later for "gulf" (and in Medieval Latin, "hollow curve or cavity in the body"). The geographic sense "large tract of water extending into the land" (larger than a bay, smaller than a sea, but the distinction is not exact and not always observed) is in English from c. 1400, replacing Old English sæ-earm. Figurative sense of "a wide interval" is from 1550s. The U.S. Gulf States so called from 1836. The Gulf Stream (1775) takes its name from the Gulf of Mexico.
"hut built by miners over a mine shaft," to store their equipment, etc., 1650s, from some source akin to Dutch kouw, German kaue in the same sense, from West Germanic *kauja-, an early borrowing of Latin cavea "hollow," from cavus "a hollow" (from PIE root *keue- "to swell," also "vault, hole").