E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
St. Nicholas. From his cradle he is said to have manifested
marvellous indications of piety, and was therefore selected for
the patron saint of boys. (Fourth century.) Boy Bishop. The
custom of choosing a boy from the cathedral choir, etc., on St.
Nicholas Day (December 6th), as a mock bishop, is very ancient.
The boy possessed episcopal honour for three weeks, and the rest
of the choir were his prebendaries. If he died during the time
of his prelacy, he was buried in pontificalibus. Probably the
reference is to Jesus Christ sitting in the Temple among the
doctors while He was a boy. The custom was abolished in the
reign of Henry VIII.