A grammarian.--Sir James Murray's New English Dictionary, 1928
To break Priscian's head, to outrage the rules of grammar.--Albert Hyamson's Dictionary of English Phrases, 1922
The phrase, "Priscian a little scratched," [Love's Labour's Lost] is a paraphrase of a common expression, "diminuis Prisciana caput," which was applied to such as speak false Latin ... It may be fairly said that from the beginning of the sixth century until recently, Priscian has reigned over Latin grammar.--John Phin's Shakespeare Cyclopædia and and Glossary, 1902
Birthday of George Fox (1624 - 1691),
founder of the Society of Friends, better known as the Quakers. Author Samuel Butler, though an adherent to the rules of the Roman grammarian Priscian, lampooned Fox and his followers in his satrical epic poem Hudibras (1663-1678):[They] hold no sin so deeply red
As that of breaking Prisian's head.