quimichin.

Headword: 
quimichin.
Principal English Translation: 

a mouse, a rodent (see Molina); also: small, dwarf, or baby (see Karttunen)

IPAspelling: 
kimitʃ
Alonso de Molina: 

quimichin. raton.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 90r. col. 1. Thanks to Joe Campbell for providing the transcription.

Frances Karttunen: 

QUIMICH-IN pl: QUIMICHTIN ~ QUIQUIMICHTIN ~ QUIMICHI-MEH mouse / ratón (M) The alternate plural QUIMICHIMEH from M is the standard one for X and is built on MICHIN as a unitary stem rather than stem plus -IN absolutive suffix. It probably represents QUIMICHIMMEH with nasal assimilation and reduction of the resulting geminate consonant. QUIMICH-IN is used as a diminutive meaning 'small, dwarf, baby,’ as in Z with the local word for opossum to mean 'baby opossum.'
Frances Karttunen, An Analytical Dictionary of Nahuatl (Norman: University of Oklahoma Press, 1992), 211.

Attestations from sources in English: 

1548 Nican ypan xihuitl yn huel otlaquimichcualoc = 1548 Here in this year things were really eaten up by mice
Here in This Year: Seventeenth-Century Nahuatl Annals of the Tlaxcala-Puebla Valley, ed. and transl. Camilla Townsend, with an essay by James Lockhart (Stanford: Stanford University Press, 2010), 72–73.

Quimich = Mouse, a name given to a child
Fray Bernardino de Sahagún, Primeros Memoriales, ed. Thelma D. Sullivan, et al. (Norman: University of Oklahoma Press, 1997), 254.

Ma quimichpil oconatlic. Iquac mitoa: intla itla oticpeoaltica, auh zan no onitlacauh = Possibly a mouse drank it. This is said when we are fighting for something and giving up.
Thelma D. Sullivan, "Nahuatl Proverbs, Conundrums, and Metaphors, Collected by Sahagún," Estudios de Cultura Náhuatl 4 (1963), 112–113.

themes: 
Animals, Bugs, Insects, Reptiles, Fish, etc.