Green’s Dictionary of Slang

1. incapacitated through drink .

1882

Aldershot Military Gaz. 16 Sept. 8/1: [He] took a few drops of whiskey, which he foolishly mixed with beer, and so got ‘all a’cock’ (laughter).

2. defeated, overthrown.

1886		Sporting Life (London) 26 Oct. 2/1: Confusion is worse confounded, and what seemed to be ‘good goods’ in the morning is knocked all a-cock at night.
1894		Hull Dly Mail 2 Oct. 4/2: He gives as a spicy ‘skit’ of Royalty; ‘knocks the Nineteenth Century all a-cock’.
1909		J. Ware Passing Eng. of the Victorian Era.