flannelmouth means one who speaks in an unclear, muffled, or sluggish manner. Lexicurio rates it Sui generis — a strength score of 88 out of 100.
Etymology
From flannel + mouth.
noun
- One who speaks in an unclear, muffled, or sluggish manner.“"Oh!—Oh!—Oh!" Bert screamed, with every blow she struck "Hey, old flannel-mouth! Watch out! You'll get yours in a second."”
- One who speaks in a glib manner with the intent of deceiving or manipulating others.“Uncle Sedgwick, who is considered around and about as somewhat of a flannelmouth, has talked Drizzlepuss into going ice fishing. . . . Uncle can tell you some wonderful fish stories, but, boy, I've never known a guy who's so careless with the truth.”