The day before Ash Wednesday, in all English speaking countries except the United States, is called Shrove Tuesday. “To shrive” (active voice), or to “be shrove” (passive) in Old English meant not only to confess one’s sins and be absolved, but to receive the advice of a spiritual counselor. Having done this, you had been “shrove.” (I do not think “shriven” is the correct past participle. If someone can correct me, please do.) The word survives today in the expression “given short shrift,” which means that the person petitioning for something, or being accused of something, was not given a full hearing. To prejudge someone of a crime, “give him short shrift and a long rope,” meant to give the accused a bogus trial and hang him.
Shrove Tuesday was also called “pancake day” in Ireland and England because all the left over fat had to be cooked with batter on this day, being that fat and dairy products were traditionally given up, along with meat, during Lent. Mardi Gras, is, as you know, a French term meaning “Fat Tuesday.” The tradition was the same in France, all fat had to be finished off by Ash Wednesday. Carnival is derived from the Latin “carne vale,” which means “good bye to meat.” The fact that the traditional Christian carnival has degenerated, in places like New Orleans and Rio de Janeiro, into a day of debauchery, is a corruption of what once was, for the most part, innocent, festive celebrating the day before Lent began.