Green’s Dictionary of Slang

(UK Und.) a fool, a dunce.

1674		Head Canting Academy (2nd edn) 177: Nizie A Fool, or Coxcomb.
1691		N. Ward ‘The Poet’s Ramble after Riches’ in Writings (1704) 17: God-take-me, Sir, Ise no sick Nisey, / To stand a Drub.
c.1698		B.E. Dict. Canting Crew n.p.: Nizy, c. a Fool, or Coxcomb.
1709		N. Ward Compleat and Humorous Account of Remarkable Clubs (1756) 107: The Fortuneless Maukin [...] may decoy the amorous Nisey into the matrimonial Shackles.
1710		Galloper 1: That their Looks may deceive the more credulous Nizies [N].
1825		Pierce Egan’s Life in London 2 Jan. 389/1: London [...] where the Nizys are done Brown without a fee.
1737, 1759, 1760, 1776		Bailey Universal Etym. Eng. Dict. [as cit. c.1698].
1754		Scoundrel’s Dict. 17: A Fool or Coxcomb – Nizie.
1859		Hotten Dict. of Modern Sl. etc. 181: nizzie a fool, a coxcomb. Old cant,.
1864, 1867, 1870		Hotten Sl. Dict.
1873		Sl. Dict.
1889–90		Barrère & Leland Dict. of Sl., Jargon and Cant.
1890–1904		Farmer & Henley Sl. and Its Analogues.
1920		Ade Hand-made Fables 203: Any poor Nizzie who thought he could operate a Theater in a Delicatessen.