Green’s Dictionary of Slang

(UK Und.) one of a team of four swindlers operating the barnard’s law under barnard n.; their task was to stand at the door and keep watch, then create a diversion under cover of which the rest of the gang escape.

1591		Greene Notable Discovery of Coosnage in Grosart (1881–3) X 11: Then standeth the Rutter at the doore, and draweth his sword and picketh a quarrell at his owne shadowe.
1592		T. Kyd Soliman and Perseda A4: A daring Rutter made a challenge.
1608		Dekker Belman of London F: The Rutter is as arrant a knaue as the rest, his part is discharged, when hee hath begun a fray with his owne shadow, whilst the rest [...] steale out of sight.