The name Aguiar is toponymic, which means that it's taken from the name of a place. It means"resting pace of the eagle" and it is a Galician name. Galicia is a region in the northwest of Spain. It's people are of a Celtic stock, and they speak a language which became the basis for Portuguese. One of the first documented use of the name was of a greek general in Spain by the name of Baltasar, who took on the surname after becoming mayor of the town of San Isidro de Aguiar. If you need more info feel free to contact me.