Green’s Dictionary of Slang

a foolish, foppish dandy.

1685		J. Crowne Sir Courtly Nice [title].
c.1698		B.E. Dict. Canting Crew.
c.1699		N. Ward ‘A Trip to New England’ in Writings (1704) 180: ’Tis difficult to find a Man neat enough for a Valet to Sir Courtly Nice.
1709		N. Ward Compleat and Humorous Account of Remarkable Clubs (1756) 91: The Sir Fopling Flutters and Sir Courtly Nices are no sooner met, but there is such tiffling of Wigs, wiping of Shoes, brushing of Stockings and managing of Faces.
1731		Chickens Feed Capons 16: Yet for all this be but a Man of Clouts, a meer Sir-courtly-Nice.
1783		Dublin Eve. Post 8 May 1/1: You are solicited by the thorough-paced hack of every Administation,and by the cringing complaisance of Sir Courtly Nice.
[1900		Bulletin (Sydney) 6 Oct. 3/2: The syrup and softness, the blushes and lies, / Of Guilt that is modest, of cringing Pretence, / The meekness, the blandness, the sly hungry eyes / Of Sir Overnice, who is vain, and damned dense?].