Green’s Dictionary of Slang

bully! excl.

excellent!

1861		‘Camp Phrases’ Chicago Trib. 11 Nov. 2: ‘Bully’ is the highest term of commendation.
1868		H.L. Williams Black-Eyed Beauty 36: Oh! you peppered the big Johny Bull of a moll! Good for you! Bully!
1884		J. Miller Memorie and Rime 163: ‘Ride? Yes; all gentlemen can ride.’ ‘Bully!’.
1891		T.B. Reed Cock House Fellsgarth 48: ‘[T]hat’ll be seven off their side [...] and one more to us — bully!’.
1892		H. Nisbet Bushranger’s Sweetheart 37: Bully, my boys!
1910		‘O. Henry’ ‘A Night in New Arabia’ in Strictly Business (1915) 223: Bully! you’re all right, Cele.
1922		S. Lewis Babbitt (1974) 145: Bully! Corking! You had a lot of pep.
1931		C.S. Montanye ‘Tight Spot’ in Complete Stories 15 Sept. 🌐 Bully! We’ll leave at once.
1989		H. Harrison Bill [...] on the Planet of Robot Slaves (1991) 201: ‘Your puissant knights did hurtle to the attack [...].’ ‘Bully!’.