What is the origin of the idiom "proud as a peacock" and when to use it?

The phrase "proud as a peacock" originated in English literature during the 14th century and refers to someone who is excessively proud or boastful, drawing comparison to the vibrant display of a peacock's feathers. This idiom is used informally to describe individuals who are excessively proud or boastful, often seeking attention or admiration from others.