Cihuacoatl.

Headword: 
Cihuacoatl.
Principal English Translation: 

a deity, literally "female serpent," an earth goddess; also referred to the second highest political office in the Tenochcan Mexica political structure, after the tlahtoani
Susan Kellogg, Law and the Transformation of Aztec Culture, 1500-170 (Norman and London: University of Oklahoma Press, 1995), 222; and Fray Bernardino de Sahagún, Primeros Memoriales, ed. Thelma D. Sullivan, et al. (Norman: University of Oklahoma Press, 1997), 105.

IPAspelling: 
siwɑːkoːɑːtɬ
Frances Karttunen: 

CIHUĀCŌĀ-TL title of a high Aztec Office / magistrado supremo que juzgaba en último instancia y cuyo poder igualaba casi siempre el del soberano, por cuya razón ha sido equiparado a un virrey o lugarteniente (S) [(1) BF.10r]. The single attestation is in the honorific form CIHUĀCŌĀTZIN-TLI. The literal sense is ‘female snake.’ See CIHUA-TL, CŌĀ-TL.
Frances Karttunen, An Analytical Dictionary of Nahuatl (Norman: University of Oklahoma Press, 1992), 34.

Attestations from sources in English: 

Snake-woman (Ciuacoatl) would appear before men covered in white chalk and had obsidian ear plugs, sometimes also golden ear plugs. She dressed in white. She wore the Nahua woman's hairstyle that involved her braids wound around her head with two points (horn-like) above her head. Somewhat reminiscent of La Llorona of legend later in Mexican history, "by night she walked weeping and wailing, a dread phantom foreboding war." Her face was painted half red and half black. Her headdress was made of eagle feathers. She wore a cape and carried a "turquoise-colored weaving-stick." (central Mexico, sixteenth century)
Fr. Bernardino de Sahagún, Florentine Codex: General History of the Things of New Spain; Book 1 -- The Gods; No. 14, Part 2, eds. and transl. Arthur J. O. Anderson and Charles E. Dibble (Santa Fe and Salt Lake City: School of American Research and the University of Utah, 1950), 4.

cihuacoatl (noun) = a magistrate of high rank; lit., "woman serpent"
Daniel Garrison Brinton, Ancient Nahuatl Poetry: Containing the Nahuatl Text of XXVII Ancient Mexican Poems (1887), 152.

Ipan muchiuh, i çioacoatl qujqua piltzintli coçolco onoca vmpa azcaputzalco = In his time, it came to pass that [the demon] Ciuacoatl ate a small boy [as] he lay in his cradle there in Azcapotzalco. (central Mexico, sixteenth century)
Fr. Bernardino de Sahagún, Florentine Codex: General History of the Things of New Spain; Book 8 -- Kings and Lords, no. 14, Part IX, eds. and transl. Arthur J. O. Anderson and Charles E. Dibble (Santa Fe and Salt Lake City: School of American Research and the University of Utah, 1951), 8.

Çã no iehoatl ipan mochiuh cioacoatl chocatinenca ioaltica, mochi tlacatl qujcaquja in chocaia qujtoaia. Nonopilhoantzitzi ic çan ie namechnocaujlia = In the days of this same [ruler] it happened that [the demon] Ciuacoatl went about weeping, at night. Everyone heard it wailing and saying: "My beloved sons, now I am about to leave you." (central Mexico, sixteenth century)
Fr. Bernardino de Sahagún, Florentine Codex: General History of the Things of New Spain; Book 8 -- Kings and Lords, no. 14, Part IX, eds. and transl. Arthur J. O. Anderson and Charles E. Dibble (Santa Fe and Salt Lake City: School of American Research and the University of Utah, 1951), 3.

çioacoatzintli (cihuacoatzintli) = serpent woman
Fray Bernardino de Sahagún, Primeros Memoriales, ed. Thelma D. Sullivan, et al. (Norman: University of Oklahoma Press, 1997), 197.

Thirteen judges named as working with the highest ruler on the most difficult legal cases: Ciuacoatl (Cihuacoatl), Tlacochcalcatl, Uitznauatlailotlac (Huitznahuatlailotlac), Ticociauacatl (Ticociahuacatl), Pochtecatlailotlac, Ezuauacatl (Ecihuahuacatl?), Mexicatl Tezcacoacatl, Acatliacapanecatl, Milnauatl (Milnahuatl), Atlauhcatl, Ticociauacatl (Ticociahuacatl), Ciuatecpanecatl (Cihuatecpanecatl), and Tequixquinaoacatl (Tequixquinahuacatl). (central Mexico, sixteenth century)
Fr. Bernardino de Sahagún, Florentine Codex: General History of the Things of New Spain; Book 8 -- Kings and Lords, no. 14, Part IX, eds. and transl. Arthur J. O. Anderson and Charles E. Dibble (Santa Fe and Salt Lake City: School of American Research and the University of Utah, 1951), 55.

çioacoatl tecutli = the Cioacoatl tecutli (central Mexico, sixteenth century)
Fr. Bernardino de Sahagún, Florentine Codex: General History of the Things of New Spain; Book 8 -- Kings and Lords, no. 14, Part IX, eds. and transl. Arthur J. O. Anderson and Charles E. Dibble (Santa Fe and Salt Lake City: School of American Research and the University of Utah, 1951), 74.

In the Florentine Codex, Book 6, Chapter 34, we see references to a mother newly delivered of a baby as imitating Cihuacoatl/Quilaztli. (central Mexico, sixteenth century)
Fr. Bernardino de Sahagún, Florentine Codex: General History of the Things of New Spain; Book 6 -- Rhetoric and Moral Philosophy, No. 14, Part 7, eds. and transl. Arthur J. O. Anderson and Charles E. Dibble (Santa Fe and Salt Lake City: School of American Research and the University of Utah, 1961), chapter 34, 185.

vel xicmana in tevevelli: nochpuchtzin, noxocoiouh: ca tiquauhcioatl, xicnamjquj, qujtoznequj: ximotilinj, xicmotlaehecalvili in quauhcioatl, in cioacoatl, in qujlaztli = Seize well the little shield. My daughter, my youngest one, be thou a brave woman; face it - that is, bear down; imitate the brave one Ciuacoatl, Quilaztli (central Mexico, sixteenth century)
Fr. Bernardino de Sahagún, Florentine Codex: General History of the Things of New Spain; Book 6 -- Rhetoric and Moral Philosophy, No. 14, Part 7, eds. and transl. Arthur J. O. Anderson and Charles E. Dibble (Santa Fe and Salt Lake City: School of American Research and the University of Utah, 1961), 160.

Chamotzin, noxocoiouh, quauhcioatl, tepitzin, cocotzin, nochpuchtzin: otitlacotic, otitequjt, ovetz motequjtzin: oticmonânamjqujli in monantzin, in cioapilli in quauhcioatl, in cioacoatl, in qujlaztli: otoconcujc, otoconacoc, oitlan tonac in chimalli, in tevevelli: in omomac qujman in iehoatl monantzin in cioapilli, in cioacoatl, in qujlaztli = Chamotzin, my youngest one, Quauhciuatl, little one, little dove, my beloved maiden, thou hast performed thy office, thou hast done thy work. Thy beloved task is done. Thou hast behaved in conformity with thy mother, Ciuapilli, Quauhciuatl, Ciuacoatl, Quilaztli. Thou hast taken, raised up, used the shield, the little shield, which thy beloved mother, Ciuapilli, Ciuacoatl, Quilaztli placed in thy hand (central Mexico, sixteenth century)
Fr. Bernardino de Sahagún, Florentine Codex: General History of the Things of New Spain; Book 6 -- Rhetoric and Moral Philosophy, No. 14, Part 7, eds. and transl. Arthur J. O. Anderson and Charles E. Dibble (Santa Fe and Salt Lake City: School of American Research and the University of Utah, 1961), 164.

cihuapilli Doña Martina chane ateponazco ynantzin in yn Nicolas hernandez tlacayeleltzin [...] ceme oc yehuantin yn inecauhcahuan yn itlaquillohuan yn mihtohua ytzonhuã yztihuã in ye huecauh onemico nican Mexico tenochtitlan yn cẽca otlamamauhtico yn aquin catca huehue tlacayeleltzin cihuacohuatl tlahtocapilli tenochtitlan [...] yn omoteneuh huey yaotachcauh Capitan General = the lady doña Martina, from Ateponazco, the mother of Nicolás Hernández Tlacaelleltzin [...] she is one of the descendants, called the hair and fingernails, of one who lived long ago here in Mexico Tenochtitlan, who was held in great awe, and that was the elder Tlacaellel, the Cihuacoatl, a noble of the royal dynasty of Tenochtitlan (central Mexico, 1613)
Annals of His Time: Don Domingo de San Antón Muñón Chimalpahin Quauhtlehuanitzin, James Lockhart, Susan Schroeder, and Doris Namala, eds. and transl. (Stanford: Stanford University Press, 2006), 238–9.

Cioacoatl tequanj: yoan tetzaujtl, tetetzaujanj, icnoiutl qujteittitia: ca mjtoaia, victli mecapalli, qujtemacaia, ic temotlaia. = The savage Snake-woman (Ciuacoatl), ill-omened and dreadful, brought men misery. For it was said: “She giveth men the hoe and trump-line. Thus she forceth men {to work}.” (central Mexico, sixteenth century)
Fr. Bernardino de Sahagún, Florentine Codex: General History of the Things of New Spain; Book 1 -- The Gods; No. 14, Part 2, eds. and transl. Arthur J. O. Anderson and Charles E. Dibble (Santa Fe and Salt Lake City: School of American Research and the University of Utah, 1950), 3.