A rich maa, a man of good substance and credit. To sport oak; to shut the outward door of a student’s room at college. An oaken towel; an oaken cudgel. To rub a man down with an oaken towel; to beat him.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
See also the definition in Nathan Bailey's 1736 dictionary of canting and thieving slang.
Oafish * OatsNathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes