turbot: [13] The turbot is etymologically the ‘thorn-flatfish’. Its name comes via Old French turbot from Old Swedish törnbut ‘turbot’. This was a compound noun formed from törn ‘thorn’ (a relative of English thorn) and but ‘flatfish’, a borrowing from Middle Low German but which probably denoted etymologically ‘stumpy’, and also supplied the final syllable of English halibut [15]. The name presumably alludes to the bony nodules on the fish’s back. => halibut, thorn
turbot (n.)
large, edible flatfish, c. 1300, from Old French turbut (12c., Modern French turbot), probably from a Scandinavian source (compare Old Swedish törnbut, from törn "thorn" + but "flatfish;" see halibut). But OED says of uncertain origin and speculates on a connection to Latin turbo "spinning top."