French culinary expression: BREAK SUGAR ON THE BACK
The meaning, at least, poses no problem for you: “to break sugar on someone's back” is to speak ill of him in his absence, when he is not there to defend himself.
But where does this funny image come from?
Which doesn't explain how this domestic necessity could have become synonymous with slander... Doubtless through the intermediary of sugar which, applied to words, became more sweet than sweet.
It is from this idea of sugary, flattering, hypocritical words that we have perhaps arrived at the phrase "to sweeten up with someone" that we find in the 18th century, which meant "the take for an imbecile", just as we will say later, in slang, "to sweeten someone up" in the sense of mistreating him - an expression which cannot be argued for our "breaking sugar on his back" since it is posterior.
In any case, mockery and slander were already very present in the symbolism of sugar and, in the absence of certainties, we are reduced to imagining that real sugar is difficult to break ("break" connoting demolition, destruction) and metaphorical sugar (hypocrisy, trickery) merged into each other to give rise to this expression, around the middle of the 19th century, “to break sugar” on someone's account and behind someone's back.
