Green’s Dictionary of Slang

1. a crown or five shillings (25p).

1859		Hotten Dict. of Modern Sl. etc. 17: caroon, five shillings. Cor. of crown.
1861		(con. 1840s–50s) H. Mayhew London Labour and London Poor III 140/1: A half-crown is a ‘metsa carroon;’ a ‘carroon’ is a crown.
1864, 1867, 1870		Hotten Sl. Dict. [as cit. 1859].
1873		Sl. Dict. [as cit. 1859].
1888		J. Runciman Chequers 78: I dicked a bar and a pash-crooner (I saw a sovereign and a half-crown).
1909		J. Ware Passing Eng. of the Victorian Era.
1936		Nottingham Eve. Post 9 Oct. 5/5: Another term [i.e. for 5s.] is ‘caroon’ of Romany origin.
2019		P. Baker Fabulosa 290/1: caroon a crown (old money).

2. (Polari) a crown, as worn.

2023

R. Milward Man-Eating Typewriter 27: novak wears [...] the caul like a caroon atop his baldy tet.