Proud as a peacock

DOES ANYONE KNOW THE MEANING OF PROUD AS A PEACOCK?

PEACOCK - "Although the word is now used for both male and female of the species, the peacock is strictly speaking the male of the peafowl, distinguished by the long, green iridescent tail that it spreads out like a fan.The male peacock's beauty and bearing led to its name becoming a synonym for a vain, self-conscious person and to the expression 'proud as a peacock." From Encyclopedia of Word and Phrase Origins by Robert Hendrickson (Facts on File, New York, 1997)