Mount, the, n. — Green’s Dictionary of Slang

Mount, the n.

1. London Bridge [one approached the Bridge up a short incline].

1718		C. Hitchin Regulator 20: The Mount, alias London Bridge.
1753		J. Poulter Discoveries (1774) 43: Stall on the Mount; stop on the Bridge.
1768		(con. 1710–25) Tyburn Chronicle II in Groom (1999) xxvi: The Mount London-Bridge.
1786		Whole Art of Thieving [as cit. 1753].

2. (Can.) Montreal.

1984

Partridge DSUE (8th edn) 758/1: C.20.

3. (N.Z. prison, also mount rock) Mount Eden Men’s Prison.

1942		M. Harcourt Parson in Prison 233: ‘The Arch’, as the prisoners called Archbishop Averill, was really loved in ‘The Mount’.
2001		D. Looser Boobslang [U. Canterbury D.Phil. thesis] 119/1: mount, the n. 1 Mount Eden Men’s Prison [...] mount rock n. Mount Eden Men’s Prison.