Definition & Meaning of "balloon head"in English

What is the origin of the term "balloon head" and how is it used?

"Balloon head" is an English slang insult that likely appeared in the 20th century, using the metaphor of a balloon—light, empty, and easily inflated—to suggest someone who is stupid, empty-headed, or foolish. The term is used in informal speech, schoolyard teasing, and comedic contexts to mock someone's intelligence or judgment. It is derogatory but mild, usually playful or humorous rather than deeply offensive.