Green’s Dictionary of Slang

the populace, the masses.

1755		Johnson Dict. Eng. Lang. (1785) n.p.: mobility [In cant language] The populace.
1771		Foote Maid of Bath in Works (1799) II 219: A little play-actor, who gets applauded or hiss’d just e’en as the mobility wills.
1788, 1796		Grose Classical Dict. of the Vulgar Tongue (2nd, 3rd edn) n.p.: Mobility. The mob: a sort of opposite to nobility.
c.1800		‘A Scene in the Election’ in C. Hindley Curiosities of Street Lit. (1871) 69: The scum of mobility [...] must be attended to.
1811		Lex. Balatronicum [as cit. 1788].
1824		Pierce Egan’s Life in London 19 Sept. 269/1: The fancy and mobility of this town made a strong muster.
1859, 1860		Hotten Dict. of Modern Sl. etc.
1864, 1867, 1870		Hotten Sl. Dict.
1882		Sydney Sl. Dict. (2 edn) 6: Mobility - The populace, the unwashed.
1895		C. Crowe Aus. Sl. Dict. 49: Mobility, the mob; opposed to nobility.