triangles, n. — Green’s Dictionary of Slang

triangles n.

[due to the hallucinations, nothing is ‘on the square’]

delirium tremens.

1864, 1867, 1870		Hotten Sl. Dict. 261: triangles a Slang term for delirium tremens, during a fit of which everything appears out of the square.
1895		Crowe Aus. Sl. Dict. 88: Triangles, another name for delirium tremens.