etymologeek.com dictionary
English word halibut comes from Middle English *halibutt (A halibut.. Fishes similar to the halibut.).

Halibut etymology history?

Halibut detailed word origin explanation

Dictionary entryLanguageDefinition
*halibutt Middle English (enm) A halibut.. Fishes similar to the halibut.
halibut English (eng) A large flatfish of the genus Hippoglossus, which sometimes leaves the ocean floor and swims vertically.