Some studies about the territory of Arco have established that, during the Neolithic period, different populations lived in the areas of the plain of the River Sarca, founding, in the Bronze and Iron Age new settlements, although these are not well identified.
Arco itself probably has Roman origins - some scholars of the 19th century were inclined to believe that the city was the ancient "Sarraca" or "Carraca", but this has been questioned by more recent studies.
In the twelfth century Arco came under the ownership of the domain of a noble Family from Bavaria, who conquered the castle, that had probably been erected by Theodoric (454-526). This Bavarian family obtained by the official feudal investiture of Arco from the Bishop of Trento, Altemanno.
From that point on Arco was one of the places affected by the historical events that took place among various of the Ezzelini family members between the 11th century and the 13th century, until their final defeat, occurred in 1260.
In the following centuries the village, after being repeatedly looted and burned, became part of the domain of the Visconti and Scala dynasties, and the Republic of Venice.
Arco was then attached to the Austrian Empire and it was only after the end of World War I that it became part of the Kingdom of Italy, in 1918.
Origins of the name Arco
As regards the etymology, the most accredited hypothesis is that it name derives from "Arx" ("fortress"):
"[...] Arco is derived from 'arx', we see some traces of Gallic influence, as 'Arcobrigo', 'Arco Villa', 'Arco' in the Occitan language, meaning 'tower', 'rock' [...]" (See “Archivio per L'Alto Adige” [“Archive for South Tyrol”], Vol. 18, 1923: 670).
In the same "Archive" (p. 678) it is also explained (citing Duchange) what we are to understand by the term "arx":
"[...] A building like a fortified castle, where people took refuge for a time in periods of war, and which was equipped with furniture and food".