TIARA, an ornament or habit wherewith the ancient Persians covered their head; and with which the Armenians and kings of Pontus are represented on medals; these last, because they were descended from the Persians. Latin authors call it indifferently tiara and cidaris. Strabo says, the tiara was in form of a tower; and the scholiast on Aristophanes's comedy, Axines, act. 1. scene 2. affirms, that it was adorned with peacock's feathers.
The kings of Persia alone had the right of wearing the tiara straight and erect; the priests and great lords wore it depressed, or turned down on the fore-side. Xenophon in his Cyropædia says, that the tiara was sometimes encompassed with the diadem, at least in ceremonies; and had frequently the figure of a half-moon embroidered on it: others are of opinion, that the diadem was in figure of a moon, and that it was hence the tiara was called lunata: lastly, others think that the tiara itself was sometimes in form of a half-moon. In fact, it appears that there were different forms of tiaras; and Paschalius De coronis, distinguishes no less than five different kinds.
TIARA is also the name of the pope's triple crown. The tiara and keys are the badges of the papal dignity; the tiara of his civil rank, and the keys of his jurisdiction: for as soon as the pope is dead, his arms are represented with the tiara alone, without the keys. The ancient tiara was a round high cap. John XXIII. first encompassed it with a crown. Boniface VIII. added a second crown; and Benedict XII. a third.