Definition & Meaning of "spunk bubble"in English

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

Spunk bubble is a slang term that appeared in mid-20th-century English to describe a person regarded as worthless, useless, or incompetent. The term combines "spunk," slang for vitality or energy (sometimes sexual), with "bubble," suggesting emptiness or lack of substance, creating a vivid metaphor for someone with no real value or effectiveness. Historically, it was derogatory and mocking, used to ridicule or belittle someone. Today it remains informal and insulting, generally used in casual, humorous, or aggressive contexts rather than polite or neutral conversation.