Someone asked in ELU chat how one would say "mettre de l'eau dans son moulin" in English.
Can anyone explain exactly what the French understand by the expression? Is the reference to a water-powered mill, or one that might mince up poor quality meat by-products to make sausage meat, for example?
And (crucially) can anyone offer any evidence to prove or disprove my theory that the English version is in fact related to the French one?
Please note that my French isn't that good, so if your English is better than my French (very likely! :) I'd appreciate it if you could post comments/answers in English.