mexicopa.

Headword: 
mexicopa.
Principal English Translation: 

north, or toward Mexico City
(a direction given in documents from Coyoacan, which lay to the south of the city)

Rebecca Horn, Postconquest Coyoacan: Nahua-Spanish Relations in Central Mexico, 1519-1650 (Stanford: Stanford University Press, 1997), 155.

Orthographic Variants: 
mexicopahuic, hueytepecpahuic, hueytepahuic
Alonso de Molina: 

mexicopa. hazia mexico.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 55v. col. 2. Thanks to Joe Campbell for providing the transcription.

Attestations from sources in English: 

quauhtlacopa = to the south (the opposite of mexicopa), and it may have been a reference to the forest or Quauhtla (a town in Morelos).
Another document gives north as yn atlacuiyanpahuic, (toward Tacubaya) and yn ihuicpa huey tepetl (toward the great mountain, surely a reference to Mount Ajusco south of Coyoacan)
Rebecca Horn, Postconquest Coyoacan: Nahua-Spanish Relations in Central Mexico, 1519–1650 (Stanford: Stanford University Press, 1997), 155.