Green’s Dictionary of Slang

1. a crooked horse-dealer [the noise of the harness, but perhaps more f. a further SE meaning, to play with words, verbal facility being the stock-in-trade of the horse-trader].

1608		Dekker Lanthorne and Candle-Light Ch. 10: These Horse-coursers are called Iynglers, and these Iynglers hauing layd out their money on a company of Iades at some drunken Fayre, up to London they driue them, and upon the Market day into Smithfield brauely come they prancing.
c.1698		B.E. Dict. Canting Crew n.p.: Jinglers c. Horse-Coursers frequenting Country Fairs.
1725		New Canting Dict. [as cit. c.1698].
1737, 1759, 1760, 1776		Bailey Universal Etym. Eng. Dict. [as cit. c.1698].
1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue.
1811		Lex. Balatronicum.
1823		Egan Grose’s Classical Dict. of the Vulgar Tongue.

2. (US) usu. pl., money, coins [note also gingleboy n.].

1908		Baltimore Sun (MD) 20 Sept. 17/5: ‘Jinglers’ [...] ‘shiners,’ and ‘sparklers’ betoken the physical delight [of high-value coins].
1917		(con. c.1890) A. Cahan Rise David Levinsky 181: Of what use is a good heart unless he has some jinglers* to go with it? [...] *Coin, money [HDAS].
1925		in Sat. Eve. Post 3 Jan. 14: For thirty thousand jinglers [HDAS].