From the zine The La-La Theory! A Zine about Language, issue 1, "Fun with Words."
"Legend has it there was a medieval monk who always said one part of the Mass wrong. Instead of 'quod in ore sumpsiumus' (Latin for 'we have taken'), he would jumble it and say the nonsense word 'mumpsimus.' When the monk's mistake was pointed out to him, he replied that he had said it that way for forty years and wasn't about to change: 'I will not change my old mumpsimus for you new sumpsimus.' In the intervening 500 years, the word has come to refer to anyone who stubbornly sticks to their old ways even when they're wrong."
Sound like any librarians you know?
Buy this zine from Katie, or choose one of the other issues, with delicious titles like
#2: A Fancy Word For Widow
#3: Mrkgnao, or, how the animals talk in other languages
#4: Scientific German for Dreamers
#5: Blizzards, Blindfolds, Squatters and Cartoonists (and other words that were born in 1880)