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It is thought that pancakes are associated to this celebration because of the solar symbolism of their shape and color. A traditional food for Mardi Gras are sweet fried dumplings, cenci, usually served in the shape of a loose knot (a 5cm wide, 20cm long strip of dough one extremity of which is passed through a slit in its middle). In New Orleans the traditional food is king cake.
The reason that pancakes are associated with the day preceding Lent is that the 40 days of Lent form a period of liturgical fasting, during which only the plainest foodstuffs may be eaten. Therefore, rich ingredients such as eggs, milk, and sugar are disposed of immediately prior to the commencement of the fast. Pancakes and doughnuts were therefore an efficient way of using up these perishable goods, besides providing a minor celebratory feast prior to the fast itself .
The word shrove is a past tense of the English verb "shrive," which means to obtain absolution for one's sins by confessing and doing penance. Shrove Tuesday gets its name from the shriving (confessing) that Anglo-Saxon Christians were expected to do prior to receiving absolution immediately before Lent.wikipedia