-ixtla.

-ĪXTLAH postpositon before, in the presence of, contemporary with / en mi presencia o en mi tiempo (M for first pers. sg.), delante (C) [(4)Cf.21r,21v,(4)Zp.94,207] M has a printing error and reads ixilia. –ĪXTLAH is synonymous with –ĪXTLAN, which is attested in C but does not appear in M. Because of the general loss of final N and H in T, attestations from that source are ambiguous between the two. See ĪX-TLI, -TLAH.
Frances Karttunen, An Analytical Dictionary of Nahuatl (Norman: University of Oklahoma Press, 1992), 120.

-īxtlâ, -īxtlan = in the presence of
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), 504.