Question: The adopted son and heir of the founder of the Roman Principate was given what name at birth?

full_context: Document 1: Claudius: Claudius ( ; Latin: "Tiberius Claudius Caesar Augustus Germanicus" ; 1 August 10 BC – 13 October 54 AD) was Roman emperor from 41 to 54. A member of the Julio-Claudian dynasty, he was the son of Drusus and Antonia Minor. He was born at Lugdunum in Gaul, the first (and until Trajan, the only) Roman Emperor to be born outside Italy. Because he was afflicted with a limp and slight deafness due to sickness at a young age, his family ostracized him and excluded him from public office until his consulship, shared with his nephew Caligula in 37.
Document 2: Augustus (Williams novel): Born Gaius Octavius Thurinus, the young future-emperor was adopted by his great-uncle, Julius Caesar, after demonstrating promising wit and skill. After his great-uncle's assassination, Augustus (at this time known as Gaius Julius Caesar Octavianus) took vengeance upon Caesar's murderers, and through tactical political moves, became one of Rome's three “Triumvirs" alongside Marc Antony and Marcus Aemilius Lepidus. After defeating the other two triumvirs, and obtaining sole power over the Roman State, Augustus (known as "Imperator" Caesar Divi Filius), began taking measures to secure and increase his power. As a result, Augustus gave orders to exterminate Cleopatra's teenaged son, allegedly commenting, "too many Caesars is no good thing." (As it was the common belief that her son was of Julius Caesar's bloodline.) In light of such orders, Cleopatra and Marc Antony—lovers at the time—committed suicide.
Document 3: Roman emperor: The Roman emperor was the ruler of the Roman Empire during the imperial period (starting in 27 BC). The emperors used a variety of different titles throughout history. Often when a given Roman is described as becoming "emperor" in English, it reflects his taking of the title "Augustus" or "Caesar". Another title often used was "imperator", originally a military honorific. Early Emperors also used the title "princeps" (first citizen). Emperors frequently amassed republican titles, notably "Princeps senatus", "Consul" and "Pontifex Maximus".
Document 4: Julii Caesares: The Julii Caesares were the most illustrious family of the patrician "gens Julia". The family first appears in history during the Second Punic War, when Sextus Julius Caesar was praetor in Sicily. His son, Sextus Julius Caesar, obtained the consulship in 157 BC; but the most famous descendant of this stirps is Gaius Julius Caesar, a general who conquered Gaul and became the undisputed master of Rome following the Civil War. Having been granted dictatorial power by the Roman Senate and instituting a number of political and social reforms, he was assassinated in 44 BC. After overcoming several rivals, Caesar's adopted son and heir, Gaius Julius Caesar Octavianus, was proclaimed Augustus by the senate, inaugurating what became the Julio-Claudian line of Roman emperors.
Document 5: Drusus Caesar: Drusus Caesar (Latin: "Drusus Iulius Caesar Germanicus" , AD 7 – AD 33) was a member of the Julio-Claudian dynasty in the early first century AD. He was the second son of Germanicus and Agrippina the Elder. After the death of his cousin Drusus the Younger in AD 23, he and his brother Nero were promoted by the emperor Tiberius as his heirs. Their progression would be short lived: in AD 29, the feud between his family and the powerful Praetorian Prefect Sejanus led to their downfall. First, his mother and Nero were exiled, and later Drusus was imprisoned in AD 30. Their deaths allowed Germanicus' third son, Caligula, to become Rome's third emperor following the death of Tiberius in 37.
Document 6: Marcus Vipsanius Agrippa: Marcus Vipsanius Agrippa ( ; 64/62 BC – 12 BC) was a Roman consul, statesman, general and architect. He was a close friend, son-in-law, and lieutenant to Octavian and was responsible for the construction of some of the most notable buildings in the history of Rome and for important military victories, most notably at the Battle of Actium in 31 BC against the forces of Mark Antony and Cleopatra. As a result of these victories Octavian became the first Roman Emperor, adopting the name of Augustus. Agrippa assisted Augustus in making Rome a city of marble and renovating aqueducts to give all Romans, from every social class, access to the highest quality public services. He was responsible for the creation of many baths, porticoes and gardens, as well as the original Pantheon. Agrippa was also father-in-law to the second Emperor Tiberius, maternal grandfather to Caligula, and maternal great-grandfather to the Emperor Nero.
Document 7: Augustalia: The Augustalia, also known as the Ludi Augustales ("Augustan Games"), was a festival celebrated October 12 in honor of Augustus, the first Roman emperor. It was established in conjunction with an altar to Fortuna Redux to mark the return of Augustus from Asia Minor to Rome in 19 BC. The pontiffs and Vestals conducted sacrifices, and the date became a holiday "(feriae)" on the official religious calendar of Rome.
Document 8: Augustus: Augustus (Latin: "Imperātor Caesar Dīvī Fīlius Augustus" ; 23 September 63 BC – 19 August 14 AD) was the founder of the Roman Principate and considered the first Roman emperor, controlling the Roman Empire from 27 BC until his death in AD 14. He was born Gaius Octavius into an old and wealthy equestrian branch of the plebeian "gens" Octavia. His maternal great-uncle Julius Caesar was assassinated in 44 BC, and Octavius was named in Caesar's will as his adopted son and heir, then known as Octavianus (Anglicized as Octavian). He, Mark Antony, and Marcus Lepidus formed the Second Triumvirate to defeat the assassins of Caesar. Following their victory at the Battle of Philippi, the Triumvirate divided the Roman Republic among themselves and ruled as military dictators. The Triumvirate was eventually torn apart by the competing ambitions of its members. Lepidus was driven into exile and stripped of his position, and Antony committed suicide following his defeat at the Battle of Actium by Octavian in 31 BC.
Document 9: Mark Antony: Marcus Antonius (Latin: ; January 14, 83 BC – August 1, 30 BC), commonly known in English as Mark or Marc Antony, was a Roman politician and general who played a critical role in the transformation of the Roman Republic from an oligarchy into the autocratic Roman Empire.
Document 10: Assassination of Julius Caesar: The assassination of Julius Caesar was the result of a conspiracy by many Roman senators. Led by Gaius Cassius Longinus, Decimus Junius Brutus, and Marcus Junius Brutus, they stabbed Julius Caesar to death in a location adjacent to the Theatre of Pompey on the Ides of March (March 15), 44 BC. Caesar was the dictator of the Roman Republic at the time, having recently been declared "dictator perpetuo" by the Senate. This declaration made several senators fear that Caesar wanted to overthrow the Senate in favor of tyranny. The conspirators were unable to restore the Roman Republic. The ramifications of the assassination led to the Liberators' civil war and, ultimately, to the Principate period of the Roman Empire.
Document 11: Gaius Caesar: Gaius Caesar (20BC – 21 February 4AD), formally Gaius Julius Caesar (Latin: "Caius Caesar Augustus filius"), was the adopted son and heir of Augustus. He was born the son of Augustus' trusted friend and general, Marcus Vipsanius Agrippa. His name at birth was Gaius Vipsanius Agrippa, but it later changed to Gaius Julius Caesar, following his adoption out of the "Vipsanii" and into the "Julii" by Augustus. He along with his brother Lucius, born in 17BC, were intended to rule the Roman Empire together.
Document 12: History of the Roman Empire: The history of the Roman Empire covers the history of Ancient Rome from the fall of the Roman Republic in 27 BC until the abdication of the last Western emperor in 476 AD. Rome had begun expanding shortly after the founding of the Republic in the 6th century BC, though it did not expand outside of the Italian Peninsula until the 3rd century BC. Civil war engulfed the Roman state in the mid 1st century BC, first between Julius Caesar and Pompey, and finally between Octavian and Mark Antony. Antony was defeated at the Battle of Actium in 31 BC. In 27 BC the Senate and People of Rome made Octavian "imperator" ("commander") thus beginning the Principate, the first epoch of Roman imperial history usually dated from 27 BC to 284 AD; they later awarded him the name Augustus, "the venerated". The success of Augustus in establishing principles of dynastic succession was limited by his outliving a number of talented potential heirs: the Julio-Claudian dynasty lasted for four more emperors—Tiberius, Caligula, Claudius, and Nero—before it yielded in 69 AD to the strife-torn Year of Four Emperors, from which Vespasian emerged as victor. Vespasian became the founder of the brief Flavian dynasty, to be followed by the Nerva–Antonine dynasty which produced the "Five Good Emperors": Nerva, Trajan, Hadrian, Antoninus Pius and the philosophically inclined Marcus Aurelius. In the view of the Greek historian Dio Cassius, a contemporary observer, the accession of the emperor Commodus in 180 AD marked the descent "from a kingdom of gold to one of rust and iron"—a famous comment which has led some historians, notably Edward Gibbon, to take Commodus' reign as the beginning of the decline of the Roman Empire.
Document 13: Lucius Junius Brutus: Lucius Junius Brutus ( ) was the founder of the Roman Republic and traditionally one of the first consuls in 509 BC. He was claimed as an ancestor of the Roman gens Junia, including Decimus Junius Brutus and Marcus Junius Brutus, the most famous of Julius Caesar's assassins.
Document 14: Agrippa Postumus: Agrippa Postumus (26 June 12 BC – 20 August AD 14), also referred to as Postumus Agrippa, was a son of Marcus Vipsanius Agrippa and Julia the Elder. He was originally named Marcus Vipsanius Agrippa Postumus in honor of his father, who died shortly before Postumus' birth. After the deaths of his older brothers, Lucius (d. AD 2) and Gaius Caesar (d. AD 4), Postumus was adopted by his maternal grandfather, the Roman emperor Augustus. In accordance with Roman naming conventions, Postumus' name was changed to Marcus Julius Caesar Agrippa Postumus. At the time Augustus considered Postumus as a potential successor, but banished him from Rome in 9AD, for reasons that remain unknown. This, in effect, though not in law, cancelled his adoption and virtually assured Tiberius' position as Augustus' sole heir. Postumus was ultimately executed by his own guards shortly after Augustus' death in AD 14.
Document 15: August: August is the eighth month of the year in the Julian and Gregorian calendars, falling between July and September, and the fifth month to have the length of 31 days. It was originally named "Sextilis" in Latin because it was the sixth month in the original ten-month Roman calendar under Romulus in 753 BC, and March was the first month of the year. About 700 BC, it became the eighth month when January and February were added to the year before March by King Numa Pompilius, who also gave it 29 days. Julius Caesar added two days when he created the Julian calendar in 45 BC, giving it its modern length of 31 days. In 8 BC, it was renamed in honor of Augustus. According to a Senatus consultum quoted by Macrobius, he chose this month because it was the time of several of his great triumphs, including the conquest of Egypt.
ground_truth: Gaius Vipsanius Agrippa