Principal English Translation: 

a reflexive indefinite prefix; impersonal of "mo" in the reflexive; refers to a general thing or person, people); can mean something like, "to each other"

Alonso de Molina: 

Ne. yo pronombre.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, f. 64r.

Horacio Carochi / English: 

ne- = indefinite reflexive prefix
Horacio Carochi, S.J., Grammar of the Mexican language with an explanation of its adverbs (1645), translated and edited with commentary by James Lockhart, UCLA Latin American Studies Volume 89 (Stanford: Stanford University Press, UCLA Latin American Center Publications, 2001), 507.

Lockhart’s Nahuatl as Written: 

This was once reciprocal.
James Lockhart, Nahuatl as Written: Lessons in Older Written Nahuatl, with Copious Examples and Texts (Stanford: Stanford University Press and UCLA Latin American Studies, 2001), 226.

Attestations from sources in English: 

Neittalo = People see each other; Neilnāmico = People remember each other; Neilcāhualo = People forget each other; Neilpilo = People bind themselves
Michel Launey, An Introduction to Classical Nahuatl, translated and adapted by Christopher MacKay (Cambridge: Cambridge University Press, 2011), 145.