cozoyahualolli.

Part of the headdress of early Aztec rulers (Noguez 1978, 34), it was circular and fan-like in an upright position with hanging paper streamers. The roots are probably coztic, or yellow, yahualolli, something round, a noun derived from the verb yahualoa, and therefore might be translated as "yellow round thing."
Justyna Olko, Turquoise Diadems and Staffs of Office: Elite Costume and Insignia of Power in Aztec and Early Colonial Mexico (Warsaw: Polish Society for Latin American Studies and Centre for Studies on the Classical Tradition, University of Warsaw, 2005), 147.

The cozoyaualolli was a rosette of scarlet macaw feathers, symbolic of fire. It was worn by Acamapichtli, Huitzilihuitl, and Chimalpopoca, the first three Mexica rulers. (central Mexico, sixteenth century)
Thelma Sullivan, "Tlatoani and tlatocayotl in the Sahagún manuscripts," Estudios de Cultura Nahuatl 14 (1980), 225–238. See esp. p. 234.

icozoyahualol ACAMAPICHTLI mitl iyehuatilma itolicpal = su escarapela amarilla, ACAMAPICHTLI, flechas, su manta de piel, su asiento de espadañas (centro de México, s. XVI)
Víctor M. Castillo F., "Relación Tepepulca de los señores de México Tenochtitlan y de Acolhuacan," Estudios de Cultura Náhuatl 11 (1974), 183–225, y ver la pág. 194—195.