Green’s Dictionary of Slang

1. an all-purpose appellation, linked to a variety of occupations; see knight of the... n.

c.1561		Awdeley Fraternitye of Vacabondes in Viles & Furnivall (1907) 8: This nimble fingred knight [...] commeth in as one not knowen of these Cheatours.
c.1595		Shakespeare Love’s Labour’s Lost V ii: Some mumble-news, some trencher-knight, some Dick.
1753		Dict. of Love n.p.: knights-errant This name was given to a set of hardy adventurers, whose professions was to run about the world in quest of broken bones, to redress wrongs done to widows, orphans, to the honour of ladies, or gentle damsels.
1836		A. Thornton Don Juan in London II 25: Some of the combatants were ‘floored’ – others looked as if a Knight of the Knuckle had made the claret spin from their day-lights.
1859		Hotten Dict. of Modern Sl. etc. 57: knight a common and ironical prefix to a man’s calling; thus, ‘knight of the whip,’ a coachman ‘knight of the thimble,’ a tailor.
1864, 1867, 1870		Hotten Sl. Dict.
1895		C. Crowe Aus. Sl. Dict. 42: Knight, an ironical prefix to a man’s calling, as a‘knight of the thimble,’ a tailor.

2. (UK Und.) ‘a poor silly fellow’ (Sinks of London, 1848).

a.1790		H.T. Potter New Dict. Cant (1795).
1809		G. Andrewes Dict. Sl. and Cant.
1821		Flash Dict.
1835		G. Kent Modern Flash Dict.
1841		‘Never Cut Your Toe Nails On Sunday’ Dublin Comic Songster 280: While Miss Cundy so smart, / Disappointed of having this short knight, / Without delay got her another sweetheart.
1854		T. Buckley Sydenham Greenfinch 66: A splitting headache rewarded our three knights for the exploits of the previous evening.