Green’s Dictionary of Slang

hypnotist n.

[hype v.1 (2) + pun]

(US campus) an eccentric.

[US]Eble Campus Sl. Nov. 5: hypnotist – a crazy person.
[US]Eble Sl. and Sociability 79: Among the slang items that seem to derive their humor from the polysyllabic Latin- and Greek-based elements of the vocabulary are [...] hypnotist ‘crazy person’.