ayocuan.

AYOCUAN(1). Yellow-winged Cacique (Cacicus melanicterus) [FC: 21 Aioquan] Two quite different birds are so named. The first listed is described as “… a forest-dweller… in the province of Cuextlan and in Michoacan. The bill is pointed, black; everywhere [over the body] its feathers are black, but its tail is mixed white [and black], so that it is called ayoquan.” Martin del Campo identified it as the “Mexican Cacique, Cassiculus melanicterus.” He argues that it was the only species approximating the description, noting, however, that the tail feathers are black and yellow, not white (1940: 388). I note here only that the currently accepted name for this species is Yellow-winged Cacique.
Fr. Bernardino de Sahagún, Florentine Codex: General History of the Things of New Spain; Book 11 – Earthly Things, no. 14, Part XII, 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, 1963); Rafael Martín del Campo, “Ensayo de interpretación del Libro Undecimo de la Historia General de las Cosas de Nueva España de Fray Bernardino de Sahagún – 11 Las Aves (1),” Anales del Instituto de Biología Tomo XI, Núm. 1 (México, D.F., 1940); and, with quotation selections, synthesis, and analysis here also appearing in E. S. Hunn, "The Aztec Fascination with Birds: Deciphering Sixteenth-Century Sources," unpublished manuscript, 2022, cited here with permission.

AYOCUAN2, Northern Jacana (Jacana spinosa) [FC: 21 Aioquan] The next species listed is also named Ayoquan, but it is “a water bird…. yellow-billed, green of wing-bend, its flight feathers, its tail are [as if] shot with mirror stones – mingled with white. Everywhere [over its body] its feathers are ruddy. The bill is pointed…” (21). No identification is offered for this species, though Martin del Campo suggested it could be the Agami Heron (Agamia agami) (1940: 389). However, that heron is rather rare and solitary and is restricted to the Atlantic lowlands. I would hazard to guess that the bird so named is more likely the Northern Jacana.
Fr. Bernardino de Sahagún, Florentine Codex: General History of the Things of New Spain; Book 11 – Earthly Things, no. 14, Part XII, 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, 1963); Rafael Martín del Campo, “Ensayo de interpretación del Libro Undecimo de la Historia General de las Cosas de Nueva España de Fray Bernardino de Sahagún – 11 Las Aves (1),” Anales del Instituto de Biología Tomo XI, Núm. 1 (México, D.F., 1940); and, with quotation selections, synthesis, and analysis here also appearing in E. S. Hunn, "The Aztec Fascination with Birds: Deciphering Sixteenth-Century Sources," unpublished manuscript, 2022, cited here with permission.

ayoquan (adjective or adverb) = nothing like it, unequaled
Daniel Garrison Brinton, Ancient Nahuatl Poetry: Containing the Nahuatl Text of XXVII Ancient Mexican Poems (1887), 150.

dos pájaros diferentes tienen este nombre (ver Hunn, arriba)