E. De Stefani notes that it is a Friulian microtoponymic surname, derived from the dialectal word broili, which in Friulian designates an enclosed orchard adjacent to the house, in turn coming from the Gaulish term brogilos. From the same etymon derive the French surnames Bruel and Breuil, as well as the sibling surname Brollo, attested in Tolmezzo, in Friuli-Venezia Giulia, with its own distribution.

Rossoni agrees in noting the Celtic origin of the term —which in its form brogilos designated an orchard or garden, or an enclosed hunting territory— and confirms that Broili is a surname peculiar to Friuli-Venezia Giulia, of very rare presence. He adds that the related form Broilo is peculiar to Trentino-Alto Adige on the border with the Vicenza area, while Brollo appears more widespread in the Veneto, in the Venice and Treviso areas, and also in Friuli in the Udine and Pordenone areas.

On the antiquity of the surname, De Stefani documents its presence in Siaio —a hamlet of Treppo Carnico, today Treppo Ligosullo, in the Carnia, a mountainous area of northern Friuli— from at least the beginning of the 14th century. Rossoni, for his part, dates the transformation into a surname in that same region to 1608.