Mumpsimus

Mumpsimus is a noun that refers to a traditional notion adhered to despite clear evidence that it is wrong. It also describes a person who obstinately clings to old habits or customs, even after they have been shown to be irrational or incorrect. Essentially, it's the stubborn refusal to abandon an error. The term carries a connotation of pedantry and intellectual rigidity. It's often used to criticize adherence to outdated traditions or procedures.

The word "mumpsimus" originated from a story about an illiterate priest who, during the celebration of Mass, incorrectly read "quod ore sumpsimus" (what we have taken in our mouths) as "quod ore mumpsimus." When corrected, he refused to change, declaring that he would not abandon his "old mumpsimus" for their "new sumpsimus." This anecdote, though possibly apocryphal, provides the etymological foundation for the word's meaning of clinging stubbornly to error. The term gained wider currency in the 16th century thanks to its use by Erasmus. Its antonym is Sumpsimus, which means a correct phrase mistakenly substituted for a wrong one.