Simon-pure is a noun that means a completely authentic person.
Our word of the day comes from 18th century satirical play called Bold Stroke for a Wife. The name Simon-pure came to mean ‘authentic’ partly because the character is impersonated by someone else for most of the play and is only revealed to be ‘authentic’ when when the real Simon-pure identifies himself. Also the character is a Quaker preacher who is ‘authentic’ in the sense of being ‘honest.’
Today the word is often used in a sarcastic sense. For example: Desmond comes across like such a Simon-Pure, but I think it’s all a facade. Deep down, he’s just as devious as anyone else.