To be compared with a parrot or popinjay in the Middle Ages, when the bird was a beautiful rarity, was a high compliment. John Lydgate in 1430 addressed the Blessed Virgin Mary in this way:
"O popinjay, plumed with al clennesse."
But when the bird became more common, his coat could be considered merely gaudy, his mimicry vulgar.
The modern popinjay is a vulgarly ostentatious person. For other words that have the intrusive n see