Green’s Dictionary of Slang

1. to give up a share, lit. ‘dole up’.

1864, 1867, 1870		Hotten Sl. Dict.
1876		C. Hindley Life and Adventures of a Cheap Jack 28: I have known men literally give their goods away, or to throw them at each other, which is termed ‘dolloping’.

2. (Irish) to adulterate.

1910		P.W. Joyce Eng. As We Speak It In Ireland (1979) 248: That coffee is dolloped.
1997		Share Slanguage.