From Wiktionary, the free dictionary
From coin + -y.
coiny (comparative coinier, superlative coiniest)
- (archaic, slang) wealthy; rich
1892, F. Anstey, Mr. Punch's Model Music-hall Songs and Dramas, page 34:So I 'anded over thirty bob, though not a coiny bloke. / I couldn't tell a Marchioness how nearly I was broke!