Green’s Dictionary of Slang

1. (UK Und., also outside pal) a lookout.

1861		H. Mayhew London Labour and London Poor IV 287/1: The other two confederates had taken up a position opposite the house, being what is termed ‘look-out’ or outside men.
1895		C. Crowe Aus. Sl. Dict. 55: Outside Pal, the thief who watches during the robbery.
1911		D. Runyon ‘The Informal Execution of Soupbone Pew’ in From First to Last (1954) 67: I always tell my outside men that, when they have to do shooting, not to try to hit anyone.
1926		J. Black You Can’t Win (2000) 98: He was an industrious and trustworthy yegg who made his living serving as ‘target’ or outside man, for the yegg mobs that preyed on country banks.
1938		F.D. Sharpe Sharpe of the Flying Squad 151: She was acting as look out or ‘outside man’ for two expert safe breakers.
1949		Monteleone Criminal Sl. (rev. edn).
1950		Goldin et al. DAUL 150/1: Outside man. 1. A lookout.
1969		D. Pendleton Executioner (1973) 119: My outside man would get nervous if I moved out of his sight.
1977		D. Powis Signs of Crime 195: Outside Man Lookout man for criminals but particularly for a ‘firm’ of card sharps engaged in the three-card trick. Such lookout men may be posted as far as 200 yds away from the venue of the action.
1989		J. Morton Lowspeak.

2. (orig. US, also outside guy) that member of a confidence trick team who locates potential victims, lures them deeper into the hoax, and helps to fleece them; the ‘steerer’ for a brothel.

1853		Mt. Echo 30 Apr. 1/5: The Vermonter examined the watch carefully, and the bidding among the outside Funks assumed an aspect of profound interest [DA].
1905		F. Hutchison Philosophy of Johnny the Gent 66: ‘It’s been noised about that you was his outside guy an’ that you was in an in wit wot come off when them drunks fell into his gig’.
1940		D. Maurer Big Con 14: The outsideman would slip several hundred dollars out of the satchel and surreptitiously give them to the mark.
1947		AS XXII 165: The outside-man nudges the mark, raises the shell slightly, and shows the mark that the pea is there. It is a sure-thing bet [DA].
1953		A.J. Liebling Honest Rainmaker (1991) 33: I was to be the outside man, or talker.
1969		‘Iceberg Slim’ Pimp 34: I been working for Aunt Kate’s house for many years now as her outside man.
1999		E. Bunker Mr Blue 111: The conversation that ensued was essentially a scripted dialogue between the inside and outside man, with an occasional nudge or whisper to the mooch by the inside man.