Q From An AOL subscriber: This is probably desperately simple but perhaps you could please tell me from where the phrase ‘butter wouldn’t melt in his mouth’ originates?
A It’s one of those sayings that are so old their origins are lost in the proverbial mists of time. It refers dismissively to somebody who appears gentle or innocent while typically being the opposite. A typical use was in William Makepeace Thackeray’s Pendennis: “When a visitor comes in, she smiles and languishes, you’d think that butter wouldn’t melt in her mouth: and the minute he is gone, very likely, she flares up like a little demon, and says things fit to send you wild”.
It appeared in print first in John Palsgrove’s book about the French language, Lesclarcissement de la Langue Françoyse of 1530, but it’s more than likely he was borrowing a saying that was already proverbial.
Since putting butter in one’s mouth, even in these technological times straight from the fridge, is certain to cause it to melt, the saying is not altogether easy to understand. It might be tied up with the idea of coolness, of a nonchalant ease that is unaffected by passion or emotion (a sense of cool that goes back at least a century before the first recorded appearance of the butter saying). If you are that coolly insouciant, the idea seems to be, butter really won’t melt in your mouth.
While looking into the phrase, I found several examples that showed that people sometimes misunderstand it. For example, this appeared in the Independent newspaper on 28 September 2001: “ ‘You’d think butter wouldn’t melt in his mouth,’ said a neighbour. ‘It’s hard to imagine he would be involved with the things he has been accused of.’ ” The speaker thinks it refers to a sweet temperament, not the misleadingly demure appearance of a person who is a lot less harmless than he or she looks. There’s nothing new about this, since the same associations are in Thomas Chandler Haliburton’s Nature and Human Nature of 1855: “He looks so good, all the women that see him say, ‘Ain’t he a dear man?’ He is meekness itself. Butter wouldn’t melt in his mouth. He has no pride in him”.