Green’s Dictionary of Slang

(UK Und.) a notorious perjurer, one who earns a living by giving false evidence.

1592		Greene Blacke Bookes Messenger 9: An auncient coossener, and one that had a long time beene a Knight of the Post.
1607		A Knight’s Conjuring Ch. I B2: This was a knight forsworne, a poore knight [...] a knight of the Post.
1613		Dekker Devil’s Last Will and Testament E: Two Knights, who are my sworne seruants and are of the Post.
1620		J. Taylor ‘Praise of Hemp-Seed’ in Works (1869) III 73: The sixt, a post-knight that for fiue groats gaine / Would sweare & and for foure groats forsweare’t againe.
c.1637		R. Brome Damoiselle III i: He takes me for a common Bail; a Knight o’th’ Post.
1641		R. Brome Jovial Crew Act I: He was taken up a Knight o’ the Post; and so he continued, till he was degraded at the whipping-post.
1651		T. Randolph Hey for Honesty I i: The thriving trades of this age we live in, namely to be a sequestrator, or pettifogger [...] or belonging to knights o’ th’ post.
1667		R. L’Estrange (trans.) Visions of Quevedo 324: How many false Witnesses, and Knights of the Post, would set their Consciences like Clocks.
1675		Head Art of Wheedling 280: He had variety of knights of the Post at his command.
1681		‘A Pangyrick’ in Ebsworth Bagford Ballads (1878) II 869: The Doctor’s busie now at work, / With his knew Knights o’ th’ Post i’ th’ dark.
1699		N. Ward London Spy VIII 194: He is so well read in Physiognomy, that he knows a Knight of the Post by his Countenance.
a.1704		T. Brown Comical View of London and Westminster in Works (1760) I 152: Knights of the post to be had in the Temple-walks from morning till night, for two pots of belch and a six-penny slice of boil’d beef.
1713		W. King York Spy 18: I presently knew these to be a sort of Rake-hells call’d Knights of the Post.
1724		A. Ramsay Tea-table Misc. (1733) IV 374: I was once an attorney at law, And after a knight of the post.
1732		‘An Irish Wedding’ in A. Carpenter Verse in Eng. in 18C Ireland (1998) 113: From Knights of the Post, against Innocents swearing / [...] / Good Lord deliver us.
1737, 1759, 1760, 1776		Bailey Universal Etym. Eng. Dict. n.p.: Knight of the Post. c. a Mercenary common Swearer, a Prostitute to every cause, an Irish Evidence.
1749		Smollett (trans.) Adventures of Gil Blas II 137: This young fellow is a knight of the post, you may depend upon it, and I arrest him and his comrade.
1751		Smollett Peregrine Pickle (1964) 625: The fugitive had been cajoled by a certain knight of the post.
1776		Caledonian Mercury 23 July 3/3: In the most fashionable circles [...] sharpers, gamblers, knights of the post, divorced harlots and demi-reps.
1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue.
1809		G. Andrewes Dict. Sl. and Cant.
1811		Lex. Balatronicum.
1824		‘Geoffrey Crayon’ Tales of a Traveller (1850) 147: The bold knights of the Post have all dwindled down into lurking footpads and sneaking pickpockets.
1835		G. Kent Modern Flash Dict.
1848		Flash Dict. in Sinks of London Laid Open.
1859		Matsell Vocabulum.
1895		C. Crowe Aus. Sl. Dict. 42: Knight of the Post, a person that will swear anything for money.