Dictionary.net

• All at a gulp: altogether.

1899 - The american dictionary of the english language.
By Daniel Lyons

• h[=o]l'us-b[=o]l'us, adv. all at a gulp: altogether.--n. the whole. [A vulgarism, formed from whole, most likely on the analogy of hocus-pocus; hardly conn. with bolus, a pill.]

1908 - Chambers's Twentieth Century Dictionary of the English Language
By Thomas Davidson