After the ceremony, the pope ditched his mitre and ceremonial robes and hopped into the popemobile for a spin around the square.
bishop's tall hat, late 14c., from Old French mitre, from Latin mitra "headband, turban," from Greek mitra "headband, turban," earlier a belt or cloth worn under armor about the waist, from PIE root *mei- "to tie" (cf. Sanskrit Mitrah, Old Persian Mithra-, god names; Russian mir "world, peace," Greek mitos "a warp thread"). In Latin, "a kind of headdress common among Asiatics, the wearing of which by men was regarded in Rome as a mark of effeminacy" [OED]. But the word was used in Vulgate to translate Hebrew micnepheth "headdress of a priest."
(Heb. mitsnepheth), something rolled round the head; the turban or head-dress of the high priest (Ex. 28:4, 37, 39; 29:6, etc.). In the Authorized Version of Ezek. 21:26, this Hebrew word is rendered "diadem," but in the Revised Version, "mitre." It was a twisted band of fine linen, 8 yards in length, coiled into the form of a cap, and worn on official occasions (Lev. 8:9; 16:4; Zech. 3:5). On the front of it was a golden plate with the inscription, "Holiness to the Lord." The mitsnepheth differed from the mitre or head-dress (migba'ah) of the common priest. (See BONNET.)