تعریف و معنای "[be] full of it"

What is the origin of the idiom "be full of it" and when to use it?

The origin of the idiom "be full of it" is derived from the phrase "full of shit," which refers to someone who is seen as insincere, deceptive, or overly boastful in their statements. The idiom conveys a sense of disbelief or skepticism towards what someone is saying, suggesting that their words lack credibility or sincerity. The phrase "full of it" is a toned-down version of the original phrase, replacing the explicit reference to excrement with a more general expression. It is now used to express doubt, disbelief, or a dismissive attitude towards someone's claims or statements.