E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
A corruption of hab nab, meaning have or not have, hence hit or miss, at random; and, secondarily, give or take, whence also an open defiance. A similar construction to willy nilly. (Anglo-Saxon, habban, to have; nabban, not to have.)
The citizens in their rage shot habbe or nabbe [hit or miss] at random.Holinshed: History of Ireland.
He writes of the weather hab nab [at random], and as the toy [fancy] takes him, chequers the year with foul and fair.Quack Astrologer (1673).
He is a devil in private brawls . hob nob is his word, give t or take t.Shakespeare: Twelfth Night, iii. 4.
Not of Jack Straw, with his rebellious crew.
That set king, realm, and laws at hab or nab [defiance]. Sir J. Harington: Epigram, iv.