Green’s Dictionary of Slang

a penny a time.

1850		H. Mayhew in Advocate 18 Dec. 10/1: ‘I’ll back Jem for a yanepatine’.
1859		Hotten Dict. of Modern Sl. etc. 131: YENEP-A-TIME, penny each time – term in betting.
1861		(con. 1840s–50s) H. Mayhew London Labour and London Poor I 11/2: I’ll back Jem for a yanepatine.
1870		Hotten Sl. Dict. [as cit. 1859].