grundyism: [19] The term grundyism ‘prudishness’ was based on Mrs Grundy, a character in Thomas Moreton’s play Speed the Plough 1798 who became proverbial for her extreme rigidity in matters of sexual morality. Dame Ashfield, another character in the play, when contemplating some ticklish moral dilemma would invariably ask herself ‘What would Mrs Grundy say?’.
grundyism (n.)
"social censorship of personal conduct in the name of conventional propriety," 1836, from Mrs. Grundy, prudish character in Thomas Morton's 1798 play "Speed the Plow," play and playwright otherwise now forgotten, but the line "What would Mrs. Grundy say?" became proverbial.