1754. Discoveries of John Poulter, 34. Another shall look out for a
mouth that has a horse to sell or change.
1811. Lex. Bal., s.v. Mouth. A silly fellow. A dupe. To stand
mouth; i.e., to be duped.
1819. Vaux, Memoirs, s.v. Mouth, a foolish silly person; a man who
does a very imprudent act, is said to be a rank mouth.