Definition & Meaning of "dirtbrain"in English

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

"Dirtbrain" is an English slang term that appeared in the late 20th century to describe a stupid or foolish person. It combines "dirt," suggesting filth or low value, with "brain," implying mental capacity, to create a metaphor for someone whose thinking is poor or useless. The term is used in informal, often humorous or mocking contexts, such as among friends or in casual insults. It is derogatory but generally mild, more teasing than harsh, though still intended to criticize someone's intelligence.