Found more references to historical ABCs, if anyone interested, in an article I'd overlooked, by Michel Meurger, in Fortean Studies 1
. ['Leopards of the Great Turk', pp198-209].
It largely tells of French examples (including the Beast of Gevaudan, which tinfoilpants mentioned right at the beginning of this thread), but it starts with some interesting ones in Irish and Welsh mythology.
The first is a beast that resembled a "cat as big as a year-old calf", that had burning breath and a blazing tail. Saint Abban, a Dark Ages Irish monk, threw the beastie into a lake, where it appears every seven years as a demonic cat.
This story compares with the Welsh Chapalu (also known as Palug's Cat), which was a vicious kitten, which was thrown into the sea at birth, but taken back and reared by the sons of Palug. The cat, when adult, became a man-eating monster cat!
However, the article mentions that Sister Mary Donatus in Beasts and Biards in the Lives of Early Irish Saints
(1934) puts these critters firmly in the dragon/water beast catergory, even though they are cat-like.
Another example given of this motif is in a 14th century French romance called Livre d'Artus
, in which Merlin tells King Arthur of a killer cat that came around after a peasant brought a black kitten up on his fishing rod. He reared it and (of course) it grew to monsterous proportions, killed that family, and went to live on a mountain (there's controversy whether it was over Lake Geneva or Lake du Bourget in Savoy). Arthur, god bless his soul, went and slayed it.
There's loads more examples of French cat-like legends, but Meurger quotes from an article from Michael Goss, who looked into legendary big cats in Britain:
Accounts of significantly large felines which cannot be interpreted as unusually developed wildcats or feral equivalents are curiously scarce [in britain] prior to c.1969