Principal English Translation:
Horacio Carochi / English:
-nepan- = (reciprocally)
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), 507, and see 460–61 (with n4)
Attestations from sources in Spanish:
concahuia Tepetitlan mani milli çan no atoctlalli çan in nepanmil = entrambas les doy una milpay tierra que está y es en la parte que dicen Tepetitlan, para que sea para entrambas (Xochimilco, Tlaxcala, 1569)
Vidas y bienes olvidados: Testamentos indígenas novohispanos, vol. 2, Testamentos en náhuatl y castellano del siglo XVI, eds., Teresa Rojas Rabiela, Elsa Leticia Rea López, Constantino Medina Lima (Mexico: Consejo Nacional de Ciencias Tecnología, 1999), 152–153.