Green’s Dictionary of Slang

1. (US drugs) to use a drink or drug to improve one’s feelings, e.g. inject heroin, drink wine; also as n.

1953

Kramer & Karr Teen-Age Gangs 63: I’ll get the deck and we’ll boot up.

2. (drugs) to take a narcotic.

1956		‘Vin Packer’ Young and Violent 36: Hurrying, he puts the eyedropper over the needle, and presses the fluid into his flesh. ‘C’mon, boot!’ he says to himself, grinning. ‘Boot up!’.
1998		J. Hoskison Inside 60: They think they can stop us ‘booting up’ by banning Kit Kats (because of the foil) and lighters (hence the taper).
2010		Codella and Bennett Alphaville (2011) 6: He’ll boot up, bark out vomit, and feel the high fade fast.

3. (US) to indulge in conspicuous consumption.

1957

D. Burley N.Y. Amsterdam News 24 Aug. 13: You can’t find Negroes agreed on anything except [...] having a heluva good time. In the ‘boot ’em up’ department we certainly excel.

4. (US black) to get ready for a fight.

1994

G. Smitherman Black Talk.

5. (UK black) to attack physically.

2016

A. Wheatle Crongton Knights 38: ‘This Sergio’s taking liberties! [...] Let’s boot him up!’.