Mrs Grundy is the name of an imaginary English character, who typifies the disciplinary control of the conventional

Convention (norm)

A convention is a set of agreed, stipulated or generally accepted standards, norms, social norms or criteria, often taking the form of a custom....

 proprieties of society over conduct, the tyrannical pressure of the opinion of neighbours on the acts of others. A tendency to be overly fearful of what the respectable might think is referred to as Grundyism.
The name appears in a play of Thomas Morton

Thomas Morton (playwright)

Thomas Morton was an English playwright.-Life:Morton was born in the city of Durham. He was the son of John and Grace Morton of Whickham, County Durham. He went to London to study law at Lincoln's Inn, but abandoned his studies for playwriting. For much of his life, Thomas lived in Pangbourne in...

, Speed the Plough (1798), in which one of the characters, Dame Ashfield, continually refers to what her neighbour Mrs.