Green’s Dictionary of Slang

(US) to promote or enhance, to stimulate enthusiasm.

1937		‘Variety’ AS XII:4 317: hypoing, stimulating or increasing business.
1952		Lait & Mortimer USA Confidential 254: Virginia was served with much ballyhoo in September, but was saved six months to ‘hypo’ the last act.
1963		F. Kohner Affairs of Gidget 55: I had hypoed myself into a state of mild expectancy.