Green’s Dictionary of Slang

to give a tip.

1867		Good Words 1 Mar. 184/1: Having ‘done’ Ephesus, we bakshished our caffagi, and left Aiasaluck at sunrise on the following morning.
1882		Macmillan’s Mag. (London) XLVI 167: The higher grades...were reserved for those who backsheeshed the highest [OED].
1916		‘Anzac’ On the Anzac Trail 89: We presented our prospective helpmeets with sufficient Turkish Delight to ensure them dyspepsia [and] backsheeshed their parents till they smiled sixteen to the dozen.