-oc.

Headword: 
-oc.
Principal English Translation: 

combining form of "onoc", a progressive = "is"

Lockhart’s Nahuatl as Written: 

auxiliary verb, the same as onoc.
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), 227.