three nights (see Molina) = yei (3) + yohualli (nights)
Orthographic Variants:
yeyoal
Alonso de Molina:
yeyoal. tres noches. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 35r. col. 2. Thanks to Joe Campbell for providing the transcription.