E. De Stefani explains that the surname derives from the given name Ermacora, coming from the Latin Hermacora, the name of the mythical first bishop of Aquileia, who according to tradition would have been elected by the evangelist Saint Mark in the year 50. He is the patron saint of the diocese of Aquileia —archbishopric of Udine—, celebrated on 12 July, a date associated in the peasant imaginary with hailstorms and storms. The week of that feast was popularly known as "the week of misfortunes". His cult was linked from the origin to that of Saint Fortunatus, and the Friulian form of the name is Macor.

E. Rossoni adds a complementary perspective: the surname could derive from the Latin cognomen Hermagora, in turn taken from the Greek Hermagoras, a name that refers to the famous sophist Hermagoras of Temnos of the 2nd century BC, cited by Quintilian. Nevertheless, Rossoni also gathers the hypothesis that the surname originated in the cult of the first bishop of Aquileia, a martyr and canonised saint.

As for its distribution, both authors agree that the surname is characteristic of the Udine area. De Stefani specifies that it is documented in localities such as Tarcento, Magnano in Riviera, Treppo Grande and San Giovanni al Natisone, with historical presence in the Carnia from at least the middle of the 15th century. The variant Macor is concentrated today in Trieste, Muggia and Cormons. Rossoni notes that the variant Ermagora is practically disappeared and also belongs to the Udine area.