We haven’t yet much information about the early history of Terracina: in fact, this period is well-known only through literary sources. We are not able, for obvious reasons, to verify the legend which has it that Terracina has been founded by Spartan exiles: so, we must discard the suppositions and consider only the certain data.
We know that, for sure, Terracina was first an Ausonius town: at the end of the 6th century BC, it already was under Roman influence, as evidenced by its mention in the first treaty between Rome and Carthage, which is mentioned by the Greek historian Polybius.
Later, the town was occupied by the Volscans, who changed its name from Tarracina (derived from the Greek Ταρρακινή – Tarrakiné or from the Etruscan Tarchna) in Anxur; then it was conquered again by the Romans in 406 BC and, since then, it followed the destiny of the “Urbs” over the centuries.
We can know much about the (re)conquest of Terracina of 406 BC through the work made by the historian Livy (Lat.: Titus Livius), born in Patavium (nowadays Padua) in 59 BC and dead in AD 17. Under the reign of Augustus, he wrote his monumental Ab Urbe Condita, that tells us about the history of Rome from its origins (753 BC) to the death of Drusus (AD 9). It was subdivided into 142 books, of which only the books I-X and XXI-XLV have been preserved until modern times, as well as some fragments of the other ones, which are known to us through summaries called “Periochae”.
In this particular case, we can read about the conquest of Terracina in the original text, contained in Book IV, Chapter 59, of which we report the Latin text with English translation in front.
 Interim tribunos militum in Volscum agrum ducere exercitum placuit; Cn. Cornelius unus Romae relictus. Tres tribuni, postquam nullo loco castra Volscorum esse nec commissuros se proelio apparuit, tripertito ad devastandos fines discessere. Valerius Antium petit, Cornelius Ecetras; quacumque incessere, late populati sunt tecta agrosque, ut distinerent Volscos; Fabius, quod maxime petebatur, ad Anxur oppugnandum sine ulla populatione accessit. Anxur fuit, quae nunc Tarracinae sunt, urbs prona in paludes. Ab ea parte Fabius oppugnationem ostendit; circummissae quattuor cohortes cum C. Seruilio Ahala cum imminentem urbi collem cepissent, ex loco altiore, qua nullum erat praesidium, ingenti clamore ac tumultu moenia invasere. Ad quem tumultum obstupefacti qui adversus Fabium urbem infimam tuebantur locum dedere scalas admovendi, plenaque hostium cuncta erant, et immitis diu caedes pariter fugientium ac resistentium, armatorum atque inermium fuit. Cogebantur itaque victi, quia cedentibus spei nihil erat, pugnam inire, cum pronuntiatum repente ne quis praeter armatos violaretur, reliquam omnem multitudinem voluntariam exuit armis, quorum ad duo milia et quingenti vivi capiuntur. A cetera praeda Fabius militem abstinuit, donec collegae venirent, ab illis quoque exercitibus captum Anxur dictitans esse, qui ceteros Volscos a praesidio eius loci auertissent. Qui ubi venerunt, oppidum vetere fortuna opulentum tres exercitus diripuere; eaque primum benignitas imperatorum plebem patribus conciliavit. Additum deinde omnium maxime tempestiuo principum in multitudinem munere, ut ante mentionem ullam plebis tribunorumue decerneret senatus, ut stipendium miles de publico acciperet, cum ante id tempus de suo quisque functus eo munere esset.
In the mean time, it was determined that the military tribunes should lead an army into the Volscan territory. Cneius Cornelius alone was left at Rome. The three tribunes, when it became evident that the Volscians had not established a camp any where, and that they would not venture an engagement, separated into three different parties to lay waste the country. Valerius makes for Antium, Cornelius for Ecetræ. Wherever they came, they committed extensive devastations on the houses and lands, so as to separate the Volscans: Fabius, without committing any devastation, proceeded to attack Anxur, which was a principal object in view. Anxur is the town now called Tarracinæ; a city built on a declivity leading to a morass: Fabius made a feint of attacking it on that side. When four cohorts sent round under Caius Servilius Ahala took possession of a hill which commanded the city, they attacked the walls with a loud shout and tumult, from the higher ground where there was no guard of defence. Those who were defending the lower parts of the city against Fabius, astounded at this tumult, afforded him an opportunity of applying the scaling ladders, and every place soon became filled with the enemy, and a dreadful slaughter continued for a long time, indiscriminately of those who fled and those who resisted, of the armed or unarmed. The vanquished were therefore obliged to fight, there being no hope for those who gave way, when a proclamation suddenly issued, that no persons except those with arms in their hands should be injured, induced all the remaining multitude voluntarily to lay down their arms; of whom two thousand five hundred are taken alive. Fabius kept his soldiers from the spoil, until his colleagues should come; affirming that Anxur had been taken by these armies also, who had diverted the other Volscan troops from the defence of that place. When they came, the three armies plundered the town, which was enriched with wealth of many years’ accumulation; and this generosity of the commanders first reconciled the commons to the patricians. It was afterwards added, by a liberality towards the people on the part of the leading men the most seasonable ever shown, that before any mention should be made of it by the commons or tribunes, the senate should decree that the soldiers should receive pay out of the public treasury, whereas up to that period every one had discharged that duty at his own expense.
In this regard, it’s very interesting to note the declension of the name Tarracina in its plural form (“Quae nunc TarracinAE SUNT“), which would let us presume that the city was already divided into several “boroughs” of great importance.