metlapilli.

Headword: 
metlapilli.
Principal English Translation: 

hand-held grinding stone, typically used for grinding maize kernels by hand on a large flat stone; the hand-held stone is usually paired (as a child to a parent) with this large flat stone, the metlatl (metate as loaned to Spanish) (see Karttunen and attestations)

IPAspelling: 
metɬɑpiːlli
Alonso de Molina: 

metlapilli. moledor con que muelen el mayz.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 55v. col. 1. Thanks to Joe Campbell for providing the transcription.

Frances Karttunen: 

METLAPĪL-LI pl: -MEH>-TIN stone rolling pin used to grind cornmeal on the metate / moledor con que muelen el maíz (M) [(1)Tp. 141, (6)Xp. 53]. See METL(A)-TL.
Frances Karttunen, An Analytical Dictionary of Nahuatl (Norman: University of Oklahoma Press, 1992), 143.

Attestations from sources in English: 

yacametlapiltic = long nose (someone with a metlapilli in terms of a nose)
Michel Launey, An Introduction to Classical Nahuatl, translated and adapted by Christopher MacKay (Cambridge: Cambridge University Press, 2011), 233.

Attestations from sources in Spanish: 

centetl metlatl metlapillo nicnomaquilia ynocihuamo Juana Francisca = un metate con su metlapil le dejo a mi nieta [sic] Juana Francisca (Toluca, 1621)
Vidas y bienes olvidados: Testamentos en náhuatl y castellano del siglo XVII, vol. 3, Teresa Rojas Rabiela, et al, eds. (México: CIESAS, 2002), 136–137.

centetl metlatl metlapilo = un metate con su metlapil (Toluca, 1621)
Vidas y bienes olvidados: Testamentos en náhuatl y castellano del siglo XVII, vol. 3, Teresa Rojas Rabiela, et al, eds. (México: CIESAS, 2002), 134–135.

themes: 
Corn, Maize
Food, Eating, Cooking
Furniture, Household Goods
Technology, Tools