Grundy
Mrs., an invisible character in Thomas Morton's comedy, Speed the Plough, published in 1798. Dame Ashfield, one of the dramatis personae, is constantly asking, "What will Mrs. Grundy say?"--but Mrs. Grundy never appears. The question has become proverbial, and "Mrs. Grundy" a synonymous term for the opinion of conventional society.
Volume II · Aiton’s Encyclopedia