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"organ of breathing in fishes," early 14c., of unknown origin, perhaps from a Scandinavian source, e.g. Old Norse giolnar which perhaps means "gills;" Old Danish -gæln (in fiske-gæln "fish gill"). Related: Gills.
liquid measure (commonly a half-pint), late 13c., from Old French gille, a wine measure, and directly from Medieval Latin gillo "earthenware jar," of uncertain origin.
Sick-looking; pale and miserable; nauseated: He was looking green around the gills, so I told him to lie down
[1930s+; the date should probably be earlier; gills, ''face,'' is found by 1626]
Looking sickly or nauseous (1959+)
in biology, type of respiratory organ found in many aquatic animals, including a number of worms, nearly all mollusks and crustaceans, some insect larvae, all fishes, and a few amphibians. The gill consists of branched or feathery tissue richly supplied with blood vessels, especially near the gill surface, facilitating the exchange of oxygen and carbon dioxide with the surrounding water. The gills may be enclosed in cavities, through which the water is often forcibly pumped, or they may project from the body into the water.