Green’s Dictionary of Slang

courageous, full of stamina and endurance.

a.1790		C. Dibdin ‘Patrick O’Row’ in Collection of Songs II 52: I’m a devil of a fellow for fame / Why I’m bottom like any game cock sir.
1812		Egan Boxiana I 26: It being considered a difficult task to beat such a bottom man as Whitaker in so short a space of time.
1820		Jack Randall’s Diary 63: If not science, I at least am bottom.
1836		D. Crockett Col. Crockett’s Exploits and Adventures in Texas (1934) 214: My little critter, who was both blood and bottom, seemed delighted.