to throw stones at someone's forehead, wounding him or her (see Molina)
Orthographic Variants:
ixquacoyonia
Alonso de Molina:
ixquacoyonia. nite. (pret. oniteixquacoyoni.) dar pedrada enla frente descalabrando a alguno. Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 47r. col. 1. Thanks to Joe Campbell for providing the transcription.