Castile (Castilla, Nahuatlized and with a locative -tlan suffix added); Castile was a kingdom of what became Spain; Caxtillan or Castillan could also refer more generically to Spain
a Spaniard (from the Spanish word, Castilla, plus the Nahuatl suffix for "person of")
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), 213.