Green’s Dictionary of Slang

(UK Und.) watching out for cabs etc. for wealthy people, in return for a tip.

1891		Bury & Norwich Post 27 Jan. 3/5: ‘I can’t go glimming, I ain’t the cheek.’ ‘Glimming?’ ‘Opening kerridge doors, guvnor’.
1912		E. Pugh City Of The World 220: They hang about outside theatres and hotels – this is known as ‘glimming’ – on the offchance of being allowed to call a cab, or to shield a lady’s dress from a muddy wheel.
1933		‘George Orwell’ Down and Out in Complete Works I (1986) 186: Paddy unexpectedly earned another eighteen pence at ‘glimming’.