Definition & Meaning of "light in the loafers"in English

What is the origin of the term "light in the loafers" and how is it used?

Light in the loafers is a slang phrase that appeared in mid-20th-century English to describe a man who is sexually impotent or lacking sexual vigor. The term uses a humorous metaphor, comparing the heaviness expected in shoes ("loafers") to sexual potency, so being "light" implies weakness or ineffectiveness. Historically, it was derogatory, used to mock or belittle men for perceived sexual inadequacy. Today it is largely historical and may be confusing to modern audiences, and using it outside humorous or historical contexts can be insulting.