quenmach.

Headword: 
quenmach.
Principal English Translation: 

what!? how?!; or, however

Orthographic Variants: 
quemmach
Alonso de Molina: 

Quemmach. como es possible? vel. es possible?
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, f. 88v.

Attestations from sources in English: 

Means the same as quen, but has more exclamation.
Robert Haskett and Stephanie Wood's notes from Nahuatl sessions with James Lockhart and subsequent research.