More on Jour Maigre from Infoplease:

• Jour Maigre - Jour Maigre (French). A day of abstinence, when meat is forbidden to be eaten. (See Banian Days.) ...
• Fish-day - Fish-day (A) [jour maigre]. A day in the Roman Catholic Church when persons, without ecclesiastical ...
• Dictionary of Phrase and Fable: J - Definitions, origins, and illustrative excerpts for words, phases, and literary allusions starting with "J"