People mark off times and celebrations in different ways. In Belgium (since 1394, in Binche), Brazil (a four-day celebration in Rio de Janeiro), Italy (in Venice, six months of celebrating in the 18th cent., now 12 days), Trinidad and Tobago (featuring a daylong competition among calypso bands), and the United States (most notably, the New Orleans), as well as other regions, people have just finished an elaborate festival (Fahlbusch, Erwin ; Bromiley, Geoffrey William: The Encyclopedia of Christianity. Grand Rapids, Mich.; Leiden, Netherlands : Wm. B. Eerdmans; Brill, 1999-<2003.).
Universally, this celebration is known as “Carnival” or Mardi Gras specifically in New Orleans. Carnival comes from a combination of Latin words meaning "farewell to the flesh." There is a great deal of irony in that name because there is by no means a time when the desires of the flesh are denied or bid farewell. Instead they are lavishly indulged. Anything goes—gluttonous eating, massive consumption of alcohol, even public displays of sexual immorality (to say nothing of what goes on behind closed doors). The streets, sidewalks, shops, and hotels on Bourbon Street in New Orleans are indeed X-rated during this festival of debauchery.
So why the name "farewell to the flesh"? Carnival or Mardi Gras coincides with the traditional last day before the fasting season that some practice as Lent, a 40-day period of self-denial and repentance, instituted by some in the early church as a way of preparing Christians for Easter. The beginning of this period is known as Ash Wednesday, so the final day of Carnival is known as Shrove Tuesday. The word "shrove" is derived from the Latin scribere, meaning, "to prescribe penance." During the middle ages, religious leaders would ensure that "shriveners" (priests) were available to hear the confessions of the multitudes of presumptuous sinners who had committed all types of iniquity during Carnival.
The job of the priest was not to call these people to a deep and true repentance, but rather to prepare them ceremonially for Lent. In other words: Have your fun! Drink as deeply as you need of the lusts of the flesh! Just be sure to confess your sins to the priest before Lent. The priest who hears your confession will prescribe fasting and the right sort of penance (self-inflicted penalty) for you to make amends with God. (Daryl Wingerd @ http://www.ccwblog.org/2009/02/heres-skinny-on-fat-tuesday.html)