We have a winner! Lol
According to Wikipedia, “Mrs Grundy originated as an unseen character in Thomas Morton’s 1798 play Speed the Plough. References to Mrs Grundy were eventually so well established in the public imagination that in Samuel Butler’s 1872 novel Erewhon, the goddess Ydgrun, an anagram for Grundy, dictates social norms.”
I first encountered her in Robert Heinlein’s sci fi when I was 12 or 13. For a couple years, I thought she was his invention. Lol!