"Matagots" or "Magician Cats" were said to bring wealth to the home where they
are well fed. According to French legend, a Matagot must be lured by a plump
chicken, then carried home without the prospective owner once looking backwards.
Then, at each meal, the Matagot must be given the first mouthful of food. In
return, it will gives its owner a gold coin each morning. In England, Dick
Whittington's cat was a Matagot who brought its owner good fortune and changed
his luck from bad to good.
-- From the Cat Snips page of Moggies, a Brit cat site. Dick Whittington was three times Mayor of London in the late 14th - early 15th century, which legend says was due to the mousing prowess of his cat and the fortune its sale brought him. Here's a long but classic version of the tale.