halibut

Halibut comes from Middle English halibut, formed from holy and butt, an old word for flatfish. The name reflects that this fish was commonly eaten on holy days.

The word has stayed remarkably steady — it began as a plain description of a fish fit for sacred occasions, and it still names that same fish today.

It's cognate with Dutch heilbot, German Heiligbutt or Heilbutt, Danish helleflynder, Swedish helgeflundra, and Norwegian Nynorsk hellefisk — all of which echo the same 'holy fish' idea in their own tongues.