Green’s Dictionary of Slang

1. Newgate prison.

1718		C. Hitchin Regulator 22: Thomas Filewood once in the Gate-House for picking a Pocket.
1831		(con. 1701) Gent.’s Mag. Jan. 52/2: They were committed to the Gate-house (Newgate) during the session.
1873		Sl. Dict.
1877		Five Years’ Penal Servitude 5: The ‘steel,’ a slang name for one of the large metropolitan prisons, as the ‘Gate’ is for Newgate.

2. Bishopsgate, London E.C.

1838		‘Paul Pry’ Oddities of London Life I 136: [T]here ain’t sitch another hooman in all the ’Gate for marketting.
1895		Mirror of Life 9 Nov. 14/2: Meacock was not only taller, but at least half a stone heavier than the lad from the ‘Gate’.

3. Billingsgate.

1846		Swell’s Night Guide 75: Bet Starks, the swell of the Gate (Billingsgate) and the chummy’s darter, are dead nuts on him.
1866		J. Greenwood Little Ragamuffin 87: I goes to the ’gate (Billingsgate) or the garden (Covent Garden) as early as four and five o’clock.
1874		H. Mayhew London Characters 322: The owners of the smacks and other boats had a strong incentive to arrive early at ‘the Gate’.
1943		R. Llewellyn None But the Lonely Heart 119: ‘Salmon’ [...] ‘I got it this morning off of a pal down the Gate,’ said Marjoriebanks.

4. Notting Hill Gate, London W11.

1956		S. Selvon Lonely Londoners 52: He and Cap used to coast Bayswater Road, from the Arch to the Gate, nearly every night.
1970		A. Sillitoe Start in Life (1979) 182: From the Arch to the Gate, through the Bush to the Scrubs.