Grundy

A person who is overly proper, prudish, or concerned with social respectability and what others think, especially about moral behavior.

From Mrs. Grundy, a character referenced in Thomas Morton's 1798 play 'Speed the Plough'. She represents propriety and social judgment without actually appearing on stage—characters constantly ask 'What will Mrs. Grundy say?' The character became so iconic that her name became a common word for prudish judgment.