Principal English Translation: 

refers to third person singular (see Molina), one who is or does something

Alonso de Molina: 

qui. denota las terceras personas de numero singular y plural.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 89v. col. 1. Thanks to Joe Campbell for providing the transcription.

Attestations from sources in English: 

-que or -queh would be the plural ending when referring to a person who is or does something; or, when used as an object, the plural is quim or quin