moca tecpin.

Headword: 
moca tecpin.
Principal English Translation: 

a place that is full of fleas (see Molina)

Alonso de Molina: 

moca tecpin. cosa llena de pulgas.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 57v. col. 1. Thanks to Joe Campbell for providing the transcription.

Attestations from sources in English: 

This is an example of a suffixless noun (no -tl, -tli, or -in ending).
Michel Launey, An Introduction to Classical Nahuatl, translated and adapted by Christopher MacKay (Cambridge: Cambridge University Press, 2011), 232.