Poppinjay is an uncommon term used to describe a vain or conceited person. It can be replaced with synonyms such as peacock, narcissist, show-off, or braggart. The term popinjay originated in the 14th century and was used to describe a parrot or bird of bright-colored feathers. Over time, it evolved to describe humans who displayed similar traits to that of a parrot - boasting, showing off their bright clothing or accessories, and being overly chatty. It is a word that is rarely used today, but its synonyms can convey the same meaning of an individual who is excessively proud or vain.