Viacom's billionaire owner wants to know who's badmouthing his girl-band pet project to The Daily Beast.
"abuse someone verbally," 1941, probably ultimately from noun phrase bad mouth (1835), in Black English, "a curse, spell," translating an idiom found in African and West Indian languages. Related: Bad-mouthed; bad-mouthing.
: If you can't say anything good, at least don't be a bad mouth
To disparage; denigrate: He bad-mouthed everybody (1930s+)