look as if butter wouldn't melt in one's mouth . look as if butter wouldn't melt in one's mouth See: BUTTER WOULDN'T MELT IN ONE'S MOUTH. No categories: add yours Source: A Dictionary of American Idioms by A. Makkai, M.T. Boatner, J.E. Gates © 2025 To section: L Subscribe to: American IdiomsIdioms feedEnglish languageHome page and general feed Comment on this entry