every two; or, two out of two; two by two; or, each one gets two (see Molina)
Alonso de Molina:
oome. cada dos, o de dos en dos, o cadavno dos. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 77v. col. 1. Thanks to Joe Campbell for providing the transcription.