turbot n.

"flat fish," c. 1300, a general Germanic name applied to various kinds of flat fishes (Old Swedish but "flatfish," German Butte, Dutch bot), from Proto-Germanic *butt-, name for a flat fish, from PIE root *bhau- "to strike." "Hence butt-woman, who sells these, a fish-wife." [OED]

large flatfish, early 15c., perhaps from hali "holy" (see holy) + butte "flatfish" (see butt (n.4)). Supposedly so called from its being eaten on holy days (compare cognate Dutch heilbot, Low German heilbutt, Swedish helgeflundra, Danish helleflynder).

Proto-Indo-European root meaning "to strike."

It forms all or part of: abut; baste (v.3) "beat with a stick, thrash;" battledore; beat; beetle (n.2) "heavy wooden mallet;" botony; boutonniere; butt (n.1) "thick end;" butt (v.) "strike with the head;" buttocks; button; buttress; confute; halibut; rebut; refute; sackbut; turbot.

It is the hypothetical source of/evidence for its existence is provided by: Latin *futare "to beat" (in compounds); Old English beadu "battle," beatan "to beat," bytl "hammer, mallet."