Green’s Dictionary of Slang

1. a £5 note.

1862

Cornhill Mag. vi 648: It is all in single pennifs on the England jug [F&H].

2. any banknote.

1891

F.W. Carew Autobiog. of a Gipsey 416: I gets clean off with the scawfer and ’bout ’er thirty quid in single pennifs and silver.