What is "feast of fools"

The Feast of Fools is the name given to a specific feast day celebrated by the clergy in Europe, initially in Northern France, but later more widely. Its later reception history has considerably obscured modern understandings of the nature and meaning of this celebration, which originated in proper liturgical observance, and has more to do with other examples of medieval liturgical drama than with either the earlier pagan (Roman) feasts of Saturnalia and Kalends or the later bourgeois lay sotie.