I'd kind of always vaguely assumed it meant being underhanded or hiding the true facts (I guess I thought that since the hat would be covering your face while you spoke through it—which, how would you talk through a thick felt hat, anyway?). But I had the definition wrong—apparently it means to talk about something you know little about, or to make up facts.
And oddly, no one seems to know where this rather stupid—well, I'll be polite and say nonsensical—phrase came from. There's some theory it had something to do with the tradition of members of the House of Lords wearing top hats, but that's pretty much dismissed as unlikely.
Did you know the correct meaning of the phrase?
