E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Tonsure (2 syl.).
The tonsure of St. Peter consists in shaving the crown and back of the head, so as to leave a ring or crown of hair.
The tonsure of James consists in shaving the entire front of the head. This is sometimes called the tonsure of Simou the Magician, and sometimes the Scottish tonsure, from its use in North Britain.