Sibyl, the name given in antiquity to certain inspired prophetesses, whether Apollo's mistresses or daughters, or merely his priestesses. The name is explained by Lactantius on authority of Varro as made up of the Doric sios = theos and bylē = boulē; Maas tries to connect it with the Eastern Saba or Sabæ; Bang makes bold to connect it with the Volva and Voluspå of the Old Norse Sagas. Their number is differently given; some writers—Ælian and Pausanias, for example—mention only four, the Erythrean, the Samian, the Egyptian, and the Sardian; Aristophanes and Plato use the word in the singular number only; but in general ten are reckoned, as by Varro—the Babylonian, the Libyan, the Delphian, the Cimmerian, the Erythrean, the Samian, the Cumæan, the Trojan or Hellespontine, the Phrygian, and the Tiburtine. Of these by far the most celebrated is the Cumæan, identified by Aristotle with the Erythrean, and personally known by the names of Herophile, Demo, Phemonoë, Deiphobe, Demophile, and Amalthæa. She figures prominently in the 6th book of Virgil's Æneid, as the conductor of the poet into the realm of the shades. Livy records the legend that she came from the east, appeared before King Tarquin, and offered him nine books for sale. The price demanded appeared so exorbitant that the king refused to purchase them. She then went away, destroyed three, and returning, asked as much for the remaining six as for the nine. This was again refused, whereupon she destroyed other three, and once more offered to sell him the remainder, but still at the same price asked at first. Tarquin was struck by her pertinacity, and bought the books, which were found to contain oracular advices regarding the religion and policy of the Romans. They were preserved in a subterranean chamber of the temple of Jupiter on the Capitoline, and were originally entrusted to two officials (duumviri sacrorum), appointed by the senate, who alone had the right to inspect them. The number of keepers was afterwards increased to ten (decemviri), and finally by Sulla to fifteen (quinddecemviri). In the year 83 B.C., the temple of Jupiter having been consumed by fire, the original Sibylline books or leaves were destroyed, whereupon a special embassy was despatched by the senate to all the cities of Greece, Italy, and Asia Minor, to collect such as were current in these regions. The new collection, of about a thousand lines, was deposited in the rebuilt temple of Jupiter, but was transferred in 12 B.C. by Augustus as pontifex to the temple of Apollo on the Palatine, where it remained till it was publicly burned by Stilicho, between 404 and 408. Many spurious Sibylline prophecies in private hands were taken by Augustus and burned. Quite distinct are the fourteen books of so-called Sibylline Oracles in Greek hexameters (over 4000 lines), a series of pretended prophecies written by Alexandrine Jews and Christians, in the interest of their faiths, and supposed to date from the 2d century B.C. down to the 3d century A.D., or, according to Ewald, even the 6th. The origin and signification of many passages have caused fierce discussion, but beyond doubt many are plainly Jewish and pre-Christian, others as plainly Christian. One passage in the eighth book (217-250) touched powerfully the imagination of that Christian world which found no difficulty in reading Messianic prophecy into the vague spirituality of the fourth eclogue of Virgil. This passage, alone in the whole series, is written acrostically, like all the Sibylline verses of Rome, the initials forming the Greek words for Jesus Christ, Son of God, Saviour, Cross. It is alluded to in the De Civitate of Augustine, and we find it again in the solemn Sequence of Thomas of Celano: 'Dies iræ, dies illa Solvet sæculum in favilla, Teste David cum Sibylla.' And it was the same sense of mysterious continuity between the ancient order and the new that gave so rich a motive to mediæval art in masterpieces by Giotto, Michelangelo, and Raphael.
Editions of these so-called Sibyllina are by Alexandre (Paris, 1841-56), a monument of erudition, the second volume with an exhaustive commentary; Friedlieb (Leip. 1852); A. Rzach (Vienna, 1891); and H. Diels (Berl. 1891). See works devoted to discussion of the question by Ewald (1858), Dechent (Zeitschr. für Kirchengesch., 1878), Badt (1869 and 1878, the latter an edition of book iv.), Maas (1879), and Bang (trans. by Poestion, 1880); also an admirable article in the Edin. Review for July 1877.