TO BREAK PRISCIAN’S-HEAD, verb. phr. (literary).—To use bad grammar. [Lat. diminuĕre Prisciani caput. Priscian a famous grammarian of the 5th century.]—GROSE (1785).

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  1527–37.  H. ELLIS, Original Letters, Illustrative of English History. [The well-known Father Forrest being ungrammatical is said to] BREKE MASTER PRECYENS HEDE.

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  1664.  BUTLER, Hudibras, II. ii. 219.

        And hold no sin so deeply red,
As that of BREAKING PRISCIAN’S HEAD.

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  1728.  POPE, The Dunciad, iii. 161.

        Some, free from rhyme or reason, rule or check,
BREAK PRISCIAN’S HEAD, and Pegasus’s neck.

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  1819.  BYRON [Life, ‘To Moore’]. Also if there be any further BREAKING OF PRISCIAN’S HEAD, will you supply the plaster.

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