popoca.

See an image that represents popoca in the Visual Lexicon of Aztec Hieroglyphs, ed. Stephanie Wood (Eugene, Ore.: Wired Humanities, 2020-present).

a comet is a star that smokes (popoca citlalin)
Here in This Year: Seventeenth-Century Nahuatl Annals of the Tlaxcala-Puebla Valley, ed. and transl. Camilla Townsend, with an essay by James Lockhart (Stanford: Stanford University Press, 2010), 65.

i Acatl xihuitl. 1363. años yquac ypan in peuh yn popocatepetl in ye popoca = The year One Reed, 1363, the time when Pocacatepetl began to smoke (central Mexico, early seventeenth century)
Codex Chimalpahin: Society and Politics in Mexico Tenochtitlan, Tlatelolco, Culhuacan, and Other Nahuatl Altepetl in Central Mexico; The Nahuatl and Spanish Annals and Accounts Collected and Recorded by don Domingo de San Antón Muñón Chimalpahin Quauhtlehuanitzin, eds. and transl. Arthur J. O. Anderson and Susan Schroeder (Norman: University of Oklahoma Press, 1997), vol. 1, 110–111.

opopocac Sitlalin yn ipocyo ytztoya yttech matlalCueyetzin = A comet appeared. Its tail faced toward Matlalcueye.
Here in This Year: Seventeenth-Century Nahuatl Annals of the Tlaxcala-Puebla Valley, ed. and transl. Camilla Townsend, with an essay by James Lockhart (Stanford: Stanford University Press, 2010), 100–101.

in moteneva in chicavac, in vapavac, in tlatolli in mitoa in chichinauhtiuh, in pupucatiuh in nelhuillo in nemaco = what are called the strong, the harsh words, which are said, burned, gave off smoke; what was spoken what was given (central Mexico, sixteenth century)
Fray Bernardino de Sahagún, Primeros Memoriales, ed. Thelma D. Sullivan, et al. (Norman: University of Oklahoma Press, 1997), 237.

In popocatiuh, in chichinauhtiuh. Inin tlatolli, itechpa mitoaya: in aquin cenca chicaoac tlatolli ic tenonotza, ioan tecoco tlatolli = He is smoking, he is sizzling. This was said of the person who reprimanded others in very harsh words, words that stung.
Thelma D. Sullivan, "Nahuatl Proverbs, Conundrums, and Metaphors, Collected by Sahagún," Estudios de Cultura Náhuatl 4 (1963), 160–161.

1689 calli xiuitl...ipan ilhuitzin concepcion opopocac citlallin (p. 800) = 1689 House year...On the day of (the Immaculate) Conception, a comet appeared. (Anales de Puebla y Tlaxcala no. 1, part 3, 1519–1691)
Frances Krug, "The Nahuatl Annals of the Tlaxcala-Puebla Region," ch. 2, p. 31. Ph.D. Dissertation draft written in the 1980s, with transcriptions and translations approved by James Lockhart. Cited here by SW.

Pupocatepel ça ca ye yuhqui pupocaticac = Popocatepetl estaba como humeando (Tlaxcala, 1662–1692)
Juan Buenaventura Zapata y Mendoza, Historia cronológica de la Noble Ciudad de Tlaxcala, transcripción paleográfica, traducción, presentación y notas por Luis Reyes García y Andrea Martínez Baracs (Tlaxcala and México: Universidad Autónoma de Tlaxcala, Secretaría de Extensión Universitaria y Difusión Cultural, y Centro de Investigaciones y Estudios Superiores en Antropología Social, 1995), 356–357.

1664 ypan meztl de junio yn opeuhqui ynic pupoca yn tepetl Popocatzin huel tomahuac yni pocyo ynicpac quizaya = en el año de 1664, en el mes de junio empezó a humear la montaña Popocatzin, un humo grueso le salía de la cima (Tlaxcala, 1662–1692)
Juan Buenaventura Zapata y Mendoza, Historia cronológica de la Noble Ciudad de Tlaxcala, transcripción paleográfica, traducción, presentación y notas por Luis Reyes García y Andrea Martínez Baracs (Tlaxcala and México: Universidad Autónoma de Tlaxcala, Secretaría de Extensión Universitaria y Difusión Cultural, y Centro de Investigaciones y Estudios Superiores en Antropología Social, 1995), 342–343.