before they became, or before they were (see Molina)
Alonso de Molina:
inayayaque. antes que tuuiesen ser, o antes que fuessen. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 38r. col. 2. Thanks to Joe Campbell for providing the transcription.