Green’s Dictionary of Slang

1. to die.

1821

Byron 1 Oct. in Letters II (1830) 541: I really think you should have more, if I evaporate within a reasonable time.

2. to leave, to vanish, to escape.

1727		Pope et al. Art of Sinking 119: Any other person [than the hero of the poem] who may be lost and evaporate in the course of the work, without the least damage to its coposition .
1797		Mrs. Radcliffe Italian I 190: I would fain prove [...] that substance can quit it as easily; I would fain evaporate through that door myself.
1845		J. Lindridge Sixteen-String Jack 116: Why, Jack, my stunner [...] ’pon honour we thought you had evaporated—mizzled, like a shower of rain!
1859		‘Timothy Titcomb’ Letters to Young People 141: If a young man should ‘kind o’ shine up to you,’ and you should ‘cotton to him,’ and he should hear you say ‘ by the jumping Moses,’ or ‘by the living jingo,’ [...] he would pretty certainly ‘evaporate’.
1861		Bell’s Life in Sydney 17 Aug. 3/2: A shoeless and filthy gamin who was evaporating through the front door.
1873		Sl. Dict.
1895		Crowe Aus. Sl. Dict. 27: Evaporated, decamped.
1915		N.Z. Truth 28 Aug. 7/7: Bill and Nellie evanporated in the direction of Napier.
1930		L. Sage Last Rustler 225: Old Roaring Bill got away with a nick. He’d evaporated out of sight.
1954		Hepster’s Dict. 3: Evaporate – Leave.