Fish, especially salmon, the cooking of which is begun while it is still alive (Cury 1390, WM 1658 etc.). Lord Macaulay's 'History of England' (1860) has "Prince George, who cared as much for the dignity of his birth as he was capable of caring for any thing but claret and calvered salmon." cf; Crimped Fish.

Original Receipt in 'The Compleat Cook' by 'WM', 1658 (WM 1658)

To make dry Salmon Calvert in the boyling.
Take a Gallon of Water, put to it a quart of Wine or Vinegar, Verjuyce or sour Beer, and a few sweet herbs and Salt, and let your Liquor boyle extream fast, and hold your Salmon by the Tayle, and dip it in, and let it have a walme, and so dip it in and out a dozen times, and that will make your Salmon Calvert, and so boyle it till it be tender.