ixcuaitl.

Headword: 
ixcuaitl.
Principal English Translation: 

the forehead (see Molina and Karttunen)

Orthographic Variants: 
īxcuāitl, ixcuatl, ixquaitl, ixquatl
IPAspelling: 
iːʃkwɑːitɬ
Alonso de Molina: 

ixquaitl. la frente dela cara.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 47r. col. 1. Thanks to Joe Campbell for providing the transcription.

ixquatl. la frente dela cara.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 47r. col. 1. Thanks to Joe Campbell for providing the transcription.

Frances Karttunen: 

ĪXCUĀ(I)-TL forehead / la frente de la cara (M) Z has the locative construction ĪXCUĀCO with the same sense. M also has the variant ixquatl. In compounds this often appears as ĪXCUAH rather than ĪXCUĀ. See ĪX-TLI, CUĀ(I)-TL.
Frances Karttunen, An Analytical Dictionary of Nahuatl (Norman: University of Oklahoma Press, 1992), 112.

Attestations from sources in English: 

in aço imixquac, in anoço incuexcochtlan, anoço iniollopan, anoço imelchiquipan, anoço imitipan, in anoço vel inxillan = the forehead, the nape of the neck, the heart, the chest, the stomach, or the whole abdomen (Mexico City, sixteenth century)
James Lockhart, We People Here: Nahuatl Accounts of the Conquest of Mexico, Repertorium Columbianum v. 1 (Los Angeles: UCLA Center for Medieval and Renaissance Studies, 1993), 146.

ixquac = by extention, can refer to the front of something
Robert Haskett and Stephanie Wood's notes from Nahuatl sessions with James Lockhart and subsequent research.

tixquamol = our eyebrows
tizquatol = our eyelids
Fray Bernardino de Sahagún, Primeros Memoriales, ed. Thelma D. Sullivan, et al. (Norman: University of Oklahoma Press, 1997), 255.

tixqua tlamama = Our forehead: It carries things on the back (central Mexico, sixteenth century)
Fray Bernardino de Sahagún, Primeros Memoriales, ed. Thelma D. Sullivan, et al. (Norman: University of Oklahoma Press, 1997), 255.

Attestations from sources in Spanish: 

ca nixquatolco yn xipehotica yuan eztli ycamac quiztoc yvan ytlancoac xipehutica = su frente estaba razpada y le salía sangre de la boca y su rodilla esta pelada (Tlaxcala, 1564)
Catálogo de documentos escritos en náhuatl, siglo XVI, vol. I (Tlaxcala: Gobierno del Estado de Tlaxcala y el Archivo Histórico del Estado de Tlaxcala, 2013), 30.