tlapia.

Headword: 
tlapia.
Principal English Translation: 

to take care of, guard, keep (see attestations); or, to be in charge (see Lockhart, attestations)

Orthographic Variants: 
tlapiya
Alonso de Molina: 

tlapia. el que guarda algo.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 131v. col. 2. Thanks to Joe Campbell for providing the transcription.

Attestations from sources in English: 

to be in charge (said of father guardians, also sometimes of governors, and of patron saints, etc.)
James Lockhart, personal communication, May 23, 2008.

motlapielitoc = is in charge (serves as patron saint)
(Mexico, late seventeenth-century) (Techialoyan manuscript from San Cristóbal Texcalucan and Magdalena Chichicaspa)
James Lockhart, personal communication, May 23, 2008.

The -toc ending is acting as a present progressive.

tlapia = is in charge (suggesting a possible alternate translation of a passage from the Cantares Mexicanos, Bierhorst, 340–41, verse 106)
James Lockhart, Nahuas and Spaniards: Postconquest Central Mexican History and Philology (Stanford: Stanford University Press, 1991), 147.

Attestations from sources in Spanish: 

motlapielia = es patrón
Anneliese Monnich, "El Altepeamatl de Ocoyacac, México," Indiana 2 (1974), 175.

motlapielia = se guarda [i.e. la imagen de la Virgen María dentro de la iglesia]
Xavier Noguez, Códice Techialoyan de San Pedro Tototepec (Estado de México), México, El Colegio Mexiquense A.C. y Gobierno del Estado de México, 1999), 40.

yn nimiznomaquiliya topilhya onpa titlapiyaz in Sant Andres Abazbatepec = te encomiende a nuestros hijos que los cuides alla en San Andres Abazbatepec (Tlaxcala, 1543)
Catálogo de documentos escritos en Náhuatl, siglo XVI, vol. I (México, Gobierno del Estado de Tlaxcala, 2013), 1.