Green’s Dictionary of Slang

a dilettante.

1774		J. O’Keeffe Tony Lumpkin in Town (1780) 28: tim: And his man Frank says he’s a dillitante? tony: Oh, he’s a great dilly.
1789		J. O’Keeffe Modern Antiques (1792) 21: You’re a Dillitante [...] a celebrated Dilli.