Word Study
halibut
CIDE DICTIONARY
halibut, n. [OE. hali holy + but, butte, flounder; akin to D. bot, G. butte; cf. D. heilbot, G. heilbutt. So named as being eaten on holidays. See Holy, Holiday.].
A large, northern, marine flatfish (Hippoglossus vulgaris ), of the family Pleuronectidæ . It often grows very large, weighing more than three hundred pounds. It is an important food fish. [1913 Webster]
OXFORD DICTIONARY
halibut, n. (also holibut) (pl. same) a large marine flat-fish, Hippoglossus vulgaris, used as food.
Etymology
ME f. haly HOLY + BUTT(3) flat-fish, perh. because eaten on holy days
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