Mumpsimuses

What’s a mumpsimus ???

It’s a phrase: a traditional custom or notion adhered to although shown to be unreasonable.

e.g “It’s a mumpsissmus!” – Robert Jones

It’s a person: one who obstinately adheres to unreasonable customs or notions.

e.g. Robert Jones
a father who stubbornly insists he is right, when everyone knows otherwise: a ‘dadsimus’

The plural?

Is it ‘Mumpisimi’? Probably not, unless you also name those large sea mammals ‘walri’ and places clowns hang out ‘circi’

Origin

Erasmus reportedly told a tale of an uneducated Catholic priest saying the mass, and while reciting the postcommunion prayer ‘Quod ore sumpsimus, Domine’ (‘What we have received in the mouth, Lord’), utters the non-word mumpsimus. Being informed of his faux pas, he persists with the phrase, whether from stubbornness, habit, or refusal to acknowledge the corrigendum. Hence the word is an example of itself.

Other Examples

“Ekspecially”
“Nukular”
“When the stars align”