iyo.

IYOH only / solo, solamente (S) This is the lexicalized third person singular preterit form of the verb. IYOĀ
Frances Karttunen, An Analytical Dictionary of Nahuatl (Norman: University of Oklahoma Press, 1992), 123.

something alone; pret. agentive noun becoming a particle. usually seen in çan iyoh, exclusively. as pret. agentive has abs. pl. iyohqueh. verb of origin now lost.
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), 222.