The Cloud Concise Dictionary of Sparkling and Strange Words presents;

Mumpsimus.

Pronunciation: 

• IPA^(key): /ˈmʌmpsɪməs/MUMP-suh-muhs

Definition: noun –  plural mumpsimuses 

1. A person who considers themselves to be absolutely correct within the parameters of any subject, despite all the full blown, twenty foot high evidence to the contrary.

2.  A person who holds such strong views, and obstinately continues to repeat their errors regardless of failure – A persistence in an erroneous use of language,memorization, practice, belief, etc., out of habit or obstinacy.

3.  Mumpsimus can describe the behavior, as well as the person doing it. Garner’s Modern American Usage says the word could describe George W. Bush because of his persistent habit of pronouncing “nuclear” as /noo-kyə-lər/ instead of the standard /noo-klee-ər/, despite the error being widely reported. (1)

Used in a sentence;

This Middle English word originally meant “an incorrigible, dogmatic old pedant,” or ‘WordPress Blogger“, but eventually came to refer to an incorrect opinion that someone clung to.

According to an old story, an illiterate 16th century clergyman used the word during mass, saying  in Latin sumpsious as mumsimus erroneously, and also writing the Latin “quod in ore mumpsimus” instead of  “quod in ore sumpsimus ” which we have taken into the mouth‘ (from the Eucharist),  The illiterate priest,  when corrected said he’d been using the word for forty years – “I will not change my old mumpsimus for your new sumpsimus” – said he.

The Oxford English Dictionary credits the English diplomat Richard Pace (1482–1536) with introducing the word, but it may have first been used by Desiderius Erasmus (1466–1536) in a letter he wrote in August 1516.  Pace acknowledged that he had taken the anecdote from Erasmus in a letter that he wrote to Erasmus in 1517. Another source attributes the tale to King Henry VII of England (1457–1509), which would make it even older.

How the long winter nights must have flown by in the those days.

Not to be confused with;

1. Sumpsimus –  A strictly correct expression or usage substituted for an old popular erro. rAdherence to or persistence in using a strictly correct term, holding to a precise practice, etc., as a rejection of an erroneous but more common form

1. Mumping –  A favourite past time of your more discerning necrophile, it involves cutting an incision into a dead body and doing the unmentionable to it, or attaching some willing participant to attach their lips to said body, whilst another incredibly strange buddy jumps upon the corpses stomach to send the contents into their friend’s mouth.

eg  “That chap is a horror,  some might call him a mumphmaster”

(I kid you not.)

1. Mumphrey – The imprint you get on your skin from tight clothes or a pillow.

eg – “Dammit, I woke up from my nap with a mumphrey on my face again!“

1. Mumphead – Someone who publicly buts in, or intrudes into a private argument or disagreement between two people and denigrates both parties. This behavior is often seen in a Pub. The Mumphead does not have to know the people arguing. He is more concerned with intruding into the conversation.

Quotes –

“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, others be too busy and curious in their new sumpsimus. Thus all men almost be in variety and discord.” – Henry V11