Green’s Dictionary of Slang

to understand; usu. in phr. do you oliver?, do you understand?

1890		Sporting Times 8 Feb. 3/2: What you want to make yourself understood is not correct French at all, but a stern look and a knuckle-duster. Then they’ll oliver to what you want quicker than a wink.
1931		‘Eng. Und. Sl.’ in Variety 8 Apr. n.p.: Oliver or tumble—Being wise to what’s happening.
1960		J. Franklyn Dict. of Rhy. Sl. 104/2: Oliver Cromwell Tumble (to understand).