E. De Stefani notes that this surname is present in the Belluno area, particularly in Sospirolo and Sedico, as well as in Friuli-Venezia Giulia, in Trieste and Grado. In the Carnia —a mountainous region of northern Friuli, in the province of Udine— the bearers of the surname are settled in Osais, a frazione of Prato Carnico. De Stefani classifies it as a toponymic surname derived from the nearby locality of Truia, also a frazione of Prato Carnico, documented from the early 14th century under the spelling in villa de Troy. The most supported etymology connects that place name with the Friulian tròi, "path". The same base would have generated other Friulian surnames of the same type, such as Troiero.

De Stefani also highlights that the forms Troiani and Troiano are related surnames with their own distribution: Troiani is attested in the Verona area, in central Italy and in the province of Bari; Troiano, in southern Italy and in urban centres of the north. For his part, E. Rossoni proposes a different reading and considers that it is a dialectal form of the medieval name Troianus, without a toponymic link.