Grandfather of Nostradamus.

Guy Gassonet, had converted to Catholicism around 1455, taking the Christian name "Pierre" and the surname "Nostredame" (the latter apparently from the saint's day on which his conversion was solemnized).

Gassonet was a court physician and Kabbalist who descended from a long line of rabbinical scholars. He was influential in his grandson's education participating in Michel Nostradamus' teaching him medicine and herbal folk medicine as well as the "forbidden" arts of Kabbalah and alchemy.