A Catholic priest, or so the story goes, was supposed to say the phrase Quod ore sumpsimus, Domine; “what we have received in the mouth, Lord”. But he misspoke, and said the nonsense-word “mumpsimus” instead of “sumpsimus”. Confronted with his error, he doubled down, continuing to use the incorrect word out of sheer stubbornness.
This story, almost certainly apocryphal, was popularised by the Dutch theologian Erasmus, who used it to make a point about those who refused to accept corrections in translations of the Bible. And so the word mumpsimus entered the general currency, used to mean a custom adhered to long after it’s shown to be unreasonable, or to refer to a person themselves who exhibits that tendency to persistently repeat a mistake.
Perhaps its most famous usage is in Henry VIII’s impassioned speech to parliament on Christmas Eve, 1545, aimed at healing the religious divisions that beset the country:
“I see and hear daily, that you of the clergy preach one against another, teach, one contrary to another, inveigh one against another, without charity or discretion. Some be too stiff in their old mumpsimus, other be too busy and curious in their new sumpsimus. Thus, all men almost be in variety and discord, and few or none do preach, truly and sincerely, the word of God, according as they ought to do.”