Green’s Dictionary of Slang

(US) to vomit.

1865		Leaves from Diary of Celebrated Burglar 22/2: A sound, as if of a person choaking, caught my ear, and it being repeated I immediately recognized my ‘chum,’ Joe, in heavy travail, leaning partly over the rail and ‘Blasting bl—dy France to h—l. H-o-o-p — what the h-o-o-p hell did I want to come h-o-o-p France for?’.
1986		C. Stroud Close Pursuit (1988) 157: One of the guys from Emergency Services hooped into his boots over it [i.e. a gruesome corpse].