Green’s Dictionary of Slang

(US campus) a silly person.

1960		(con. WWII) R. Leckie Marines! 129: I’m gonna teach you helium-heads how to shoot mortars.
1978		Crack the Sky ‘Lighten Up McGraw’ 🎵 Safety in Numbers [album] Lighten up McGraw / You’re a helium brain / Jog a mile in the rain.
1980		Eble Campus Sl. Fall 3: helium head – synonym for airhead.
1986		R. Forrest Lark 10: No, this is Oral Roberts, helium head. Who did you think it is?
a.1989		Spears NTC’s Dict. Amer. Sl. 178: Well, what’s that helium head done now?
2001		V. Lardo McNally’s Folly 90: ‘Fitz,’ I accused, ‘is a helium head.’ ‘But what a dish, eh, Archy?’.