atetl.

Headword: 
atetl.
Principal English Translation: 

a testicle; or, a rock in water (see Karttunen)

IPAspelling: 
ɑːtetɬ
Alonso de Molina: 

atetl. compañon.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 7v. col. 2. Thanks to Joe Campbell for providing the transcription.

Frances Karttunen: 

ĀTE-TL testicle, or rock in water / compañón (M), piedra del río (Z)[(1)Zp.142]. The literal sense of this is ´water-stone.´ See Ā-TL, TE-TL.
Frances Karttunen, An Analytical Dictionary of Nahuatl (Norman: University of Oklahoma Press, 1992), 13.

Attestations from sources in English: 

auh çan yehuantin ynin omoteneuhque yetlamantin teopixque, yn quil quincuallittaya tliltique ynic quincahuazquia ynic amo quinmictizquia yece macihui yn quincahuazquia yniqu intlan tliltique monemiltizquia yece quil mochintin quinmatequixtilizquia quinmatecuilizquia ynic amo campa huel oc ceme tlapilhuatizquia yntech señorati. = It was only these three said groups of religious that the blacks reportedly approved of and were going to spare and not kill; but although they were going to spare them so that they would live among the blacks, nevertheless reportedly they were going to remove and take off the testicles of all of them so that one of them somewhere couldn't have children by the Spanish women, (central Mexico, 1612)
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), 222–223.

cuitlapanaatetl = testis (central Mexico, sixteenth century)
Fr. Bernardino de Sahagún, Florentine Codex: General History of the Things of New Spain; Book 10 -- The People, No. 14, Part 11, 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), 130.

themes: 
Anatomy
Sexuality, Fertility
Stones, Masonry
Weapons, Shields, Heraldry