to have one's hands fall asleep; or, to have numbness of the hands (see Molina)
Alonso de Molina:
macepoa. no. (pret. onomacepouh.) adormecerse la mano. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 50r. col. 2. Thanks to Joe Campbell for providing the transcription.