a prudish adherence to conventionality, especially in personal behavior.
(lowercase) an instance of such prudishness.
Origin of Grundyism
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
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.
Online Etymology Dictionary, © 2010 Douglas Harper