From AD 205, when the city (civitas) and community (pagus) fused into one municipality (municipium), Dougga bore the title liberum, whose significance is not immediately clear.
The term appears in the titles of a certain number of other municipia also founded at the same time: Thibursicum Bure, Aulodes, and Thysdrus.
Several interpretations of its meaning have been suggested.
According to Merlin and Poinssot, the term derives from the name of the god Liber, in whose honor a temple was erected at Dougga.
The epithet Liberum would thus follow the same pattern as Frugifer and Concordia, which appear in the title of Thibursicum Bure.
Thibursicum Bure is however an exception to the rule; the titles of the other municipia including the term liberum do not include the names of any divinities, and this hypothesis has therefore been abandoned.
Alternatively, liberum is taken as a reference to free status (libertas, "liberty").
This interpretation is confirmed by an inscription found at Dougga that honors Alexander Severus as the "preserver of liberty" (conservator libertatis).

It is, however, unclear exactly what form this liberty took.
Toutain is of the opinion that this is a designation for a particular type of municipium—free cities where the Roman governor did not have the right to control the municipal magistrates.
There is however no evidence that Dougga enjoyed exceptional legal privileges of the type associated with certain free cities such as Aphrodisias in Asia Minor.
Veyne has thus suggested that Dougga's "freedom" is nothing but an expression of the concept of liberty without any legal meaning; obtaining the status of a municipium had freed the city of its subjugation and enabled it to adorn itself with the "ornaments of liberty" (ornamenta libertatis).
The city's liberty was celebrated just as its dignity was extolled; the emperor Probus is a "preserver of liberty and dignity" (conservator libertatis et dignitatis).
Gascou, in line with Veyne's interpretation, describes the situation thus: "Liberum, in Thugga's title, is a term […] with which the city, which had waited a long time for the status of a municipium, is happy to flatter itself".

Despite Gascou's conclusion, efforts have been made more recently to identify concrete aspects of Dougga's liberty.
Lepelley believes on the one hand that this must be a reference to the relations between the city and Rome and on the other hand that the term can cover a range of diverse privileges of differing degrees.
It is known that the territory of Carthage, to which the Dougga pagus belonged until AD 205, enjoyed such privileges: the inhabitants of the pagus even sent an appeal during Trajan’s reign to defend the fiscal immunity of the territory of Carthage (immunitas perticae Carthaginiensium).
The Dougga civitas had not been granted this concession, so the fusion of pagus with the civitas meant that the citizens of the pagus risked losing their enviable privilege.
The liberty of the municipia founded during the reign of Septimius Severus could thus be a reference to the fiscal immunity made possible by the region’s great wealth and by the emperor’s generosity to each municipium at the time of its fusion.
During the reign of Gallienus, a certain Aulus Vitellius Felix Honoratus, a well-known individual in Dougga, made an appeal to the emperor "in order to assure the public liberty".
Lepelley believes that this is an indication that the city's privilege had been called into question, although Dougga appears to have been at least partially able to preserve its concessions, as evidenced by an inscription to the honor of "Probus, defender of its liberty".

According to Christol though, this interpretation overly restricts the meaning of the word libertas.
In Christol's view, it is important not to forget that the emperor's decision in 205 must have been taken in response to a request made by the civitas and must have taken account of the relations that already existed between it and the pagus.
It was the autonomy that the civitas had achieved during the reign of Marcus Aurelius an
From AD 205, when the city (civitas) and community (pagus) fused into one municipality (municipium), Dougga bore the title liberum, whose significance is not immediately clear. The term appears in the titles of a certain number of other municipia also founded at the same time: Thibursicum Bure, Aulodes, and Thysdrus. Several interpretations of its meaning have been suggested. According to Merlin and Poinssot, the term derives from the name of the god Liber, in whose honor a temple was erected at Dougga. The epithet Liberum would thus follow the same pattern as Frugifer and Concordia, which appear in the title of Thibursicum Bure. Thibursicum Bure is however an exception to the rule; the titles of the other municipia including the term liberum do not include the names of any divinities, and this hypothesis has therefore been abandoned. Alternatively, liberum is taken as a reference to free status (libertas, "liberty"). This interpretation is confirmed by an inscription found at Dougga that honors Alexander Severus as the "preserver of liberty" (conservator libertatis).
It is, however, unclear exactly what form this liberty took. Toutain is of the opinion that this is a designation for a particular type of municipium—free cities where the Roman governor did not have the right to control the municipal magistrates. There is however no evidence that Dougga enjoyed exceptional legal privileges of the type associated with certain free cities such as Aphrodisias in Asia Minor. Veyne has thus suggested that Dougga's "freedom" is nothing but an expression of the concept of liberty without any legal meaning; obtaining the status of a municipium had freed the city of its subjugation and enabled it to adorn itself with the "ornaments of liberty" (ornamenta libertatis). The city's liberty was celebrated just as its dignity was extolled; the emperor Probus is a "preserver of liberty and dignity" (conservator libertatis et dignitatis). Gascou, in line with Veyne's interpretation, describes the situation thus: "Liberum, in Thugga's title, is a term […] with which the city, which had waited a long time for the status of a municipium, is happy to flatter itself".
Despite Gascou's conclusion, efforts have been made more recently to identify concrete aspects of Dougga's liberty. Lepelley believes on the one hand that this must be a reference to the relations between the city and Rome and on the other hand that the term can cover a range of diverse privileges of differing degrees. It is known that the territory of Carthage, to which the Dougga pagus belonged until AD 205, enjoyed such privileges: the inhabitants of the pagus even sent an appeal during Trajan’s reign to defend the fiscal immunity of the territory of Carthage (immunitas perticae Carthaginiensium). The Dougga civitas had not been granted this concession, so the fusion of pagus with the civitas meant that the citizens of the pagus risked losing their enviable privilege. The liberty of the municipia founded during the reign of Septimius Severus could thus be a reference to the fiscal immunity made possible by the region’s great wealth and by the emperor’s generosity to each municipium at the time of its fusion. During the reign of Gallienus, a certain Aulus Vitellius Felix Honoratus, a well-known individual in Dougga, made an appeal to the emperor "in order to assure the public liberty". Lepelley believes that this is an indication that the city's privilege had been called into question, although Dougga appears to have been at least partially able to preserve its concessions, as evidenced by an inscription to the honor of "Probus, defender of its liberty".
According to Christol though, this interpretation overly restricts the meaning of the word libertas. In Christol's view, it is important not to forget that the emperor's decision in 205 must have been taken in response to a request made by the civitas and must have taken account of the relations that already existed between it and the pagus. It was the autonomy that the civitas had achieved during the reign of Marcus Aurelius an
Dougga