" The Chronique de Saint-Denis "
A medieval document by a fourteenth century monk, Saint Dennis, who wrote a history of the Merovingian times.
" seen this famous Francillon "
Francillon was an enormously successful play by the French writer Alexander Dumas (1802-1870) which involved a recipe for a salad, called the Salade Francillon. You can see the recipe here. The main ingredients are mussels, truffles, champagne and boiled potatoes.
Dumas is now more famous for writing adventure novels such as The Count of Monte Cristo and The Three Musketeers.
" that gentle old anarchist Fénelon "
François Fénelon by Joseph Vivien
François Fénelon (1651-1715), was a French Catholic theologian and writer. He is remembered as an early advocate of human rights.
" I must just go and see the Duc d'Aumale "
Prince Henri, Duke of Aumale
Prince Henri, Duc d'Aumale (1822-1897) was the youngest son of Louis-Phillipe, the last king of France, and an advocate of constitutional monarchy. He was ridiculously wealthy (worth about £200 million in today's money) and amassed a collection of manuscripts and books, as well as an art collection which he bequeathed to the state. There is no direct reason why Cottard uses him as a lavatorial euphemism.
" in some fantasy of Gustave Moreau "
Moreau's Oedipus and the Sphinx
Gustave Moreau (1826-1898) was a French painter who painted mythical or Biblical subjects in the Symbolist style.