Mardi Gras

First recorded in 1690–1700; from French: literally, “fat Tuesday”

Just about everyone knows that Mardi Gras, “fat Tuesday” in French, is closely associated with the gaudy blowout in New Orleans, Mardi Gras being the day before Ash Wednesday, which is the beginning of Lent, the 40 days of prayer, fasting, and all-night partying that is so typical of New Orleans.
The day is so named from the French custom of parading a fat ox ( bœuf gras ) during the celebration of the holiday (one wonders what became of the ox). French Mardi comes from the Latin phrase Martis diēs “Mars’s day,” so named after Mars, the planet and deity of the third day of the week according to Hellenistic astrology. Gras is problematical: it ultimately derives from Latin crassus “thick, stout, plump,” and one would therefore expect cras, but French has gras, Italian grasso, Spanish and Portuguese graso, all showing g-, not c-.