The first edition of the late Alan Davidson’s wonderful Oxford Encyclopaedia of Food (1999) is still available at a reduced price from Amazon and elsewhere so there is no real need yet to go for the second edition, though this has been scrupulously expanded by Tom Jaine. The first edition has this about syllabub (or sillabub):
… a sweet, frothy confection which was popular in Britain from the 16th to the 19th centuries, and has since been revived in a small way as a dessert.
The origin of the word ‘syllabub’ is a mystery. Lexicographers find no compelling reason to accept any of the explanations offered so far.
Originally syllabub was a drink with a foamy head, but the foamy part was the object of chief interest and later became the main element. It has often been said that the primitive method of making syllabub, ensuring a good foam, was to partly fill a jug with sweetened, spiced white wine or cider and to milk a cow directly into it. When this technique was critically examined and subjected to experiments by Vicky Williams in 1996, it was found to be unsatisfactory, and it began to seem doubtful whether it had ever been a common practice.
Ivan Day crowned the debate on this particular question by a technical and historical survey of the whole subject of syllabubs, now the locus classicus. He acknowledges at the end of his essay help received (presumably on the particular question of direct milking) from cow 53 at Thrimby Manor Farm, Cumbria, as well as the illumination provided by the numerous 17th- and 18th-century authors whose recipes he cites.
I am keeping for a later post some notes from the Oxford Encyclopaedia of Food on the cooking of Canadian porcupine crackling, a subject dealt with sketchily, if at all, in modern cookbooks.