Principal English Translation: 

causitive or reflexive indicator used more with transitive verbs; with a transitive verb, usually means reverential

Lockhart’s Nahuatl as Written: 

applicative ending of verbs. also acts as causative of verbs in -ti. Class 3: -lih.

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), 223.

Attestations from sources in English: 

The formula for transitive verbs to become honorific is to have the applicative -lia suffix added (except with verbs ending in -oa, which will change to the -huia, -ilhuia, -alhuia endings). For example:
quimocāhuilia = he leaves it.
Michel Launey, An Introduction to Classical Nahuatl, translated and adapted by Christopher MacKay (Cambridge: Cambridge University Press, 2011), 215.