miles’s boy, n. — Green’s Dictionary of Slang

miles’s boy n.

[Bee (1823) cites a tax-collector called Miles, who employed a boy to check on people who might be attempting to default on their dues by moving away]

‘a very knowing lad in receipt of much information’ (B&L).

1823		‘Jon Bee’ Dict. of the Turf, the Ring, the Chase, etc. 119: Miles’s boy — ‘Who told you? I thought no one knew.’ Ans. ‘I had it from Miles’s boy.’.
1841		‘F.L.G’ Swell’s Night Guide K4: Miles’s Boy, Nobody.