Principal English Translation:
peacefully, tranquilly, slowly, little by little; carefully, with discretion, gently, sweetly; humbly (an adverb) (see Lockhart and Molina)
Alonso de Molina:
iuian. mansamente, o contiento. aduerbio.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 44r. col. 1. Thanks to Joe Campbell for providing the transcription.
Lockhart’s Nahuatl as Written:
particle. peacefully, uncontested, gradually, bit by bit. the same as matcā. from iuh/ihui, -yān?
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), 220.
Attestations from sources in Spanish:
DON HERNANDO PIMENTEL IHUIAN itlatlapaltilma itepotzoicpal = DON HERNANDO PIMENTEL IHUÍAN, su manta listada de colores, su asiento con espaldar (centro de México, s. XVI)
Víctor M. Castillo F., "Relación Tepepulca de los señores de México Tenochtitlan y de Acolhuacan," Estudios de Cultura Náhuatl 11 (1974), 183–225, y ver la pág. 214—215.