Hastings' Dictionary of the New Testament 
Caligula (‘little boots’) was a pet name given by the soldiers in his father’s army to the boy who was afterwards known officially as Gaius Caesar Germanicus. In a similar way the name ‘Caracalla’ or ‘Caracallus’ was applied popularly to Imperator Caesar Marcus Aurelius Antoninus (a.d. 198-217), and ‘Elagabalus’ to Imperator Caesar Marcus Aurelius Antoninus Augustus (a.d. 218-222). These sobriquets had no official currency, but were useful as brief ways of referring to the names of Emperors, whose ancestors by nature or adoption had names so like their own, that confusion was certain to occur in conversation or writing about them. Caligula, who was named at birth Gains Iulius Caesar, was the third son of the distinguished general Germanicus, and Agrippina (the elder). As Germanicus was a son of Drusus, the adopted son of Augustus, and as Agrippina was a daughter of (Agrippa and) Iulia, the daughter of Augustus, Caligula was thus both by nature and by adoption a great-grandson of the Emperor Augustus. He is commonly said to have been born in the camp of his father (Tac. Ann . i. 41); but Suetonius ( Gaius , 8) points out that the boy was born before his father left for his province. The date of his birth was 31 Aug., a.d. 12. From a very early time he displayed signs of the insanity which was to break out in the most signal manner when he attained to manhood. His mania took three forms-inordinate lust, inordinate vanity, and a homicidal tendency. No doubt, as in the case of other Emperors, we must allow for the influence of evil-minded gossip on our historical records, but there remains ample evidence to justify this statement. He was proclaimed Emperor on the death of his grand-uncle Tiberius on 18 March, a.d. 37. He was offered the honorary title of pater patriae in the early days of 38, and died on 24 Jan. 41 at the hands of an assassin, C. Cassius Chaerea, in one of the vaults of the palace on the Palatine Hill. He was thrice married, first to Iunia, Claudilla, daughter of a patrician, M. Silanus.*[Note: So Suet. Gaius, 12; but Bury, on what authority the present writer does not know, names Orestilla, wife of Cn. Piso, as his first wife (A History of the Roman Empire, p. 221).]She died in childbirth, and he afterwards married Lollia Paulina, daughter of M. Lollius, whom he had robbed from her husband Memmius. He soon afterwards divorced her. His third wife was Milonia Caesonia. Caligula left no descendants.
Caligula’s reign was as uneventful as it was short. The machine of government had been left in such perfect condition by Augustus and Tiberius that the recklessness of a Caligula could not in such a short time do serious harm. But one thing he could and did do: he wasted the savings of his predecessors. He succeeded to the Empire because he was the personal heir of Tiberius, not because he had been in any sense his partner in the Empire. It was the theory of the principate that it came to an end on the death of each Emperor, and that power returned to the Senate and people as in the days of the Republic; but in practice it was difficult, if not impossible, to pass over the Emperor’s heir, and Gaius was thus proclaimed Emperor. His reign began with a relaxation of many of the restrictions of Tiberius’ rule, but his only aim throughout was the pursuit of excitement and pleasure. There is no need to detail the countless variety of his insane actions. Towards the end of his principate he revived the reign of terror, which was such a feature of Tiberius’ time.
Certain changes were made in the Eastern provinces in the reign of Gaius. The territory of Antiochus of Commagene, which had been made a province by Tiberius, was restored to his son: it ran along the northern side of the province of Cilicia. Herod Agrippa received the tetrarchy of his uncle Philip, along with Abilene. Later he obtained also Samaria, after Herod Antipas and his wife Herodias had been expelled by the Emperor at his instance. Thrace was also restored to a member of the old dynasty which had ruled it. To his kinsmen Polemo and Cotys, Gaius gave Pontus Polemoniacus and Lesser Armenia respectively. The Arabian Sohaemus was made ruler over the Ituraeans. Ptolemaeus, King of Mauritania, was executed, and steps were taken to convert his kingdom into two provinces. The most useful thing Gaius did in the way of provincial government was to put the legion which was in the province of Africa under the command of an Imperial legatus . Hitherto Africa had been the only senatorial province with Roman troops in it. This legatus had also civil functions in the Numidian part of Africa.
One aspect of Caligula’s activity had a serious effect on the Jews, and thus drew forth two of the most interesting historical tractates of the Roman Empire, Philo’s Legatio ad Gaium and contra Flaccum . The Emperor claimed to be worshipped as a god. This claim was naturally rejected by the Jews of Judaea and of Alexandria. The governor of Egypt, with ill-timed zeal, required them to set up statues of Gaius in their synagogues. The riots which resulted caused many deaths. In the year a.d. 40 the Jews of Alexandria sent an embassy to the Emperor to get the governor’s decree rescinded. This embassy was unsuccessful, and but for the speedy death of the Emperor the consequences of the proposed sacrilege would have been most serious.
Literature.-The ancient authorities are Suetonius, Gaius ; Philo, contra Flaccum and Legatio ad Gaium ; Dio Cassius; etc. The relevant parts of Tacitus ( Annals , bk. vii. ff.) are lost. Modern books are J. B. Bury, A History of the Roman Empire , London, 1893, pp. 168, 214ff., etc.; V. Duruy, A History of Rome , Eng. translation, do. 1884-86, iv. 370ff. (splendidly illustrated); H. Schiller, Gesch. der röm. Kaiserzeit , Gotha, 1883, i. 304-314; A. von Domaszewski, Gesch. der röm. Kaiser , Leipzig, 1909, ii. 1-20.
Cyclopedia of Biblical, Theological and Ecclesiastical Literature 
(so called from caligce, the foot-dress of a common soldier, which he wore while his father was in the camp in Germany), properly Caius Caesar the third of the series of Roman emperors, was the youngest son of Germanicus, the nephew of Tiberius, by Agrippina. He was born Aug. 31, A.D. 12 (Suetonius, Claud. 8), and, after spending his youth among the soldiers in Germany (Tacitus, Ann. 1:41, 69; Dio Cass. 57:5), he was received into favor by Tiberius after the fall of Sejanus (A.D. 32), although his mother and brothers had been disgraced by that tyrant, whom he succeeded as emperor in March, A.D. 37. (See Tiberius). He is frequently mentioned (under the simple name "Caius") by Josephus, who speaks of his restoration of Agrippa I to his Jewish dominions (Ant. 18:7, 10) among the few acts of liberality that characterized the first months of his. reign. After his recovery from illness, however, which his excesses had brought upon him, he gave way to his naturally brutal temper in so violent and irrational a manner as to be evidence of downright insanity, and was at length assassinated Jan. 24, A.D. 41. It does not appear that he molested the Christians. He commanded Petronius, governor of Syria, to place his statue in the Temple at Jerusalem for the purpose of adoration; but the Jews so vigorously opposed it that, fearing a sedition, he suspended the order (Josephus, Ant. 17: 8). See Smith's Diet. Of Class. Ant. s.v.; Conybeare and Howson's St. Paul, 1:110, 111.
The Nuttall Encyclopedia 
Roman emperor from A.D. 37 to 41, youngest son of Germanicus and Agrippina, born at Antium; having ingratiated himself with Tiberius, was named his successor; ruled with wisdom and magnanimity at first, while he lived in the unbridled indulgence of every lust, but after an illness due to his dissipation, gave way to the most atrocious acts of cruelty and impiety; would entertain people at a banquet and then throw them into the sea; wished Rome had only one head, that he might shear it off at a blow; had his horse installed as consul in mockery of the office; declared himself a god, and had divine honours paid to him, till a conspiracy was formed against him on his return from an expedition into Gaul, when he was assassinated (12-41).