E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
A friar who served as an attendant at the gate of a monastery court. As a curtal dog was not privileged to hunt or course, so a curtal friar virtually meant a worldly-minded one.
Some do call me the curtal Friar of Fountain Dale; others again call me in jest the Abbot of Fountain Abbey; others still again call me simply Friar Tuck.Howard Pyle: The Merry Adventures of Robin Hood, ii. p. 141.