Green’s Dictionary of Slang

(Irish) a fool; a loafer.

1882		Cardiff Times 21 Oct. 2/2: ‘And what is a rodney?’ — Witness: A man who works one day, and is idle six months.
1895		J. Caminada Twenty-Five Years of Detective Life 55: He did not like working for his living, but was what is termed a ‘Rodney.’.
1909		W.H. Davies Beggars 279: My grandmother [...] must make a confidant of a thoughtless boy, or, to use her own words – ‘a little black and a rodney.’.
1948		P. Kavanagh Tarry Flynn (1965) 248: The right rodney if ever there was one. Hasn’t a thing in the suit-case except a lock of oul’ rags – and a couple of books.