flannelmouth

noun2

1. •
   (informal, old-fashioned) 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." — 1913
2. •
   (informal, old-fashioned) One who speaks in a glib manner with the intent of deceiving or manipulating others.