Definition & Meaning of "jackshitter"in English

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

Jackshitter is a slang term that appeared in mid-20th-century English to describe a person who talks confidently about a subject they barely understand. The term builds on "jack" (slang for worthless or insignificant) and "shitter" (someone producing or spreading crap), so together it labels someone as spouting nonsense. Historically, it was derogatory and mocking, used to call out ignorance or pretension, and today it remains informal, insulting, and coarse, typically used in casual or aggressive speech rather than polite conversation.