Definition & Meaning of "mush head"in English

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

"Mush head" is a slang insult that appeared in English in the 20th century, combining "mush" (soft or pulpy substance) with "head" to describe a person who is weak-minded, stupid, or confused. The metaphor likens the brain to something soft and ineffectual, emphasizing mental dullness or lack of clarity. It is used in informal, often teasing, mocking, or critical contexts, such as conversation, media, or casual writing. The term is mildly derogatory and intended to insult; its harshness depends on tone and context.