Boy Bishop, a boy chosen on 6th December, St. Nicholas' Day, generally out of the choir, to act as bishop and do all his episcopal duties, except celebrate mass. For the term of his office, which varied, he was treated as bishop, and if he died during his tenure of it was buried with episcopal honours. The term of office was limited in 1279 to 24 hours.
Definition taken from The Nuttall Encyclopædia, edited by the Reverend James Wood (1907)
“Box and Cox,” * Boyars