Green’s Dictionary of Slang

1. a type of torture using electricity.

1900		A.H. Lewis ‘The Humming Bird’ in Sandburrs 27: ‘The Humming Bird?’ I persisted. ‘What is it like?’ [...] dey sets him in d’ trough, like I says, wit’ mebby its eight inches of water in it. [...] A sawbones gets him be d’ pulse, an’ one of them ’lectrical sriffs t’rows a wire, which is one end of d’ battery, in d’ water. D’ wire, which is d’ other end, finishes in a wet sponge. An’ say! hully hell! when dey touches a poor mark wit’ d’ sponge end on d’ shoulder, or mebby d’ elbow, it completes d’ circuit, see!
1927		Clark & Eubank Lockstep and Corridor 70: They also had what was known as the humming bird. A man would be stripped and blindfolded and an electric battery applied to different parts of his body.

2. the electric chair.

1900		A.H. Lewis ‘The Humming Bird’ in Sandburrs 27: ‘The Humming Bird?’ I persisted. ‘What is it like?’ [...] It’s d’ same t’ing as d’ chair at Sing Sing, only not so warm.
1931–34		in D. Clemmer Prison Community (1940) 333/1: Hummingbird...The electric chair.
1935		A.J. Pollock Und. Speaks n.p.: Humming bird, death.