look as if butter wouldn't melt in (one's) mouth
To appear innocent or reserved in certain company, when in fact one may have the opposite demeanor. Sure, he looks as if butter wouldn't melt in his mouth when he's around people he doesn't know, but stay a while and you'll see what he's really like.
Farlex Dictionary of Idioms. © 2024 Farlex, Inc, all rights reserved.
look as if butter wouldn't melt in one's mouth
Fig. to appear to be cold and unfeeling (despite any information to the contrary). Sally looks as if butter wouldn't melt in her mouth. She can be so cruel. What a sour face. He looks as if butter wouldn't melt in his mouth.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.
look as if butter wouldn't melt in your mouth
appear deceptively gentle or innocent. informalFarlex Partner Idioms Dictionary © Farlex 2017
butter wouldn't melt (in his/her mouth), looks as if
Suspiciously coy or demure, too good to be true. This expression dates from the early sixteenth century and was already a proverb in John Heywood’s 1546 collection. It recurs again and again (Swift, Dickens, Thackeray, Shaw) and has been a cliché for at least a century.
The Dictionary of Clichés by Christine Ammer Copyright © 2013 by Christine Ammer