-on-.

Headword: 
-on-.
Principal English Translation: 

a directional away from the speaker; there (as in onpa, "allí" in Spanish); then (as in "entonces "in Spanish)

Lockhart’s Nahuatl as Written: 

directional prefix, action goes in direction away from speaker or reference point
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), 228.

Attestations from sources in English: 

This works as the opposite of -hual-.

ōmpa onquīza = he's going out for there ('emerging there from here')
Michel Launey, An Introduction to Classical Nahuatl, translated and adapted by Christopher MacKay (Cambridge: Cambridge University Press, 2011), 51.