buckhorse, n. — Green’s Dictionary of Slang

buckhorse n.

[the mid-18C pugilist Buckhorse (real name John Smith) who, for a small charge, allowed people to hit him hard on the side of the head, one result of which was the phr. ‘ugly as Buckhorse’; he was drawn by Hogarth (as ‘the Noted Bruiser’ 1847) and appears in the novel Rodney Stone (1896)]

a blow on the ear.

1860		Hotten Dict. of Modern Sl. etc. (2nd edn) 106: Buckhorse a smart blow or box on the ear; derived from the name of a celebrated ‘bruiser’ of that name.
1864		Blackwood’s Mag. in the Public Schools’ Report (1864 – Westminster School) II 463: One of the Seniors informs us that the common punishment was buckhorsing. ‘That was boxing the ears, was it?’ ‘Yes.’ ‘Buckhorsing was rather severe, was it not?’ etc. ‘I got buckhorsed pretty often’ [F&H].
1870		Hotten Sl. Dict.
1873		Sl. Dict.