Definition & Meaning of "bag of hammers"in English

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

"Bag of hammers" is an English slang expression that appeared in the 19th–20th centuries, using a vivid metaphor: a bag full of heavy, inanimate objects like hammers suggests clumsiness, dullness, or lack of mental agility. It describes a very stupid, slow-witted, or mentally inept person. The phrase is used in informal speech, comedy, and literary contexts to mock someone's intelligence or competence. It is derogatory but mild and humorous rather than vulgar or deeply offensive.