head piece, conical cap (see attestations)
copilli = conical Huastec cap, part of the cuextecatl war costume.
Olko believes copilli is not the turquoise mosaic diadem that some have argued. That is the xiuhhuitzolli.
ocelocopilli = jaguar skin conical headpiece (Tezozomoc 2001, 264)
y iocelocupil in icpac contlaliticac = on his head he has set his conical jaguar-skin headpiece
Quetzalcoatl: yn ehecatl ynteiacancauh yntlachpancauh in tlaloque, yn aoaque, yn qujqujiauhti. Auh yn jquac molhuja eheca, mjtoa: teuhtli quaqualaca, ycoioca, tetecujca, tlatlaiooa, tlatlalpitza, tlatlatzinj, motlatlaueltia. Auh yujn yn muchichioaia: ocelocopile, mjxtlilpopotz, hecanechioale, mizqujnechioale, tzicoliuhcanacoche, teucujtlaacuechcozque, quetzacoxollamamale, ocelotzitzile, icpaomjcicujle, hecacozcachimale, hecaujque, no poçulcaque. = Quetzalcoatl—he was the wind, the guide and road-sweeper of the rain gods, of the masters of the water, of those who brought rain. And when the wind rose, when the dust rumbled, and it crackled and there was a great din, and it became dark and the wind blew in many directions, and it thundered; then it was said: “{Quetzalcoatl} is wrathful.” And thus was he bedight: he had a conical ocelot-skin cap. His face was thickly smeared with soot. He was adorned with {spiral} wind and mesquite symbols. He had a curved, turquoise mosaic ear-pendant. He wore a gold neckband of small sea-shells. He had the quetzal-pheasant as a burden on his back. He had ocelot anklets with rattles. He wore a cotton bone {-ribbed} jacket. He carried the shield with the wind-shell design. He had the curved {inlaid} spear-thrower and also foam sandals. (central Mexico, sixteenth century)