Sibylla Palmifera by Dante Gabriel Rossetti
Sibyl, from Greek sibylla, meaning "prophetess," was originally a word referring to one of the ten female oracles, and they were so mystically respected that even in early Christian theology their gifts were highly regarded, or at least intriguing, and Sibyl began being used as a given name in the Middle Ages.
Sibyl also comes with a delightful list of variants, each quite beautiful. The spelling Cybil/Cybill has been used, as well as English Sybella and sometimes versions starting with a Z, such as Zibylla. Both Sibylle and Sybille have been used in France, Sibylla in Sweden, Sybille and Sibylle in German, Sibylla in Greek, Sibilla in Italian, Sybilla in Late Roman, Sébire in Norman, and my favorite - Sibyllina, as in Blessed Sibyllina Biscossi (although she may have been known as Sibila, Sibilina or Sybil).
This name has not ranked in the U.S. since 1929. In 2016 it was only given to 19 baby girls. Sybella was given to 11 girls, while the other variants were given to none.
Being such an old name, of course she has some famous namesakes. Sybil Ludington is one, a young girl noted as the female Paul Revere, who rode at night to warm American soldiers of incoming British. One of the first namesakes, however, was Sybil of Burgundy, the Queen Consort of Sicily. She was alive around the same time as Sibylla of Normandy, the Queen Consort of Scotland. Another first namesake was a 12th century noblewoman who was either daughter or niece or Hugh de Lacy. Namesakes don't really reappear until the 1800's with a few actresses and singers. A standout is witch Sybil Leek, who led a fascinating life and was famous in Britain. There are even more namesakes for Sibylle and very regal (almost exclusively) namesakes for Sibylla.
In literary works, Sybil Vane was a character in Oscar Wilde's The Picture of Dorian Gray. There are three books titled Sybil, and two The Sybil. Sybil is a character in the Harry Potter world and the Discworld series.
There are three films titled "Sybil." There is an English operetta Sybil, which is a version of Victor Jacobi's Szibill. "The Song of the Sybil" is a Gregorian chant sung in Majorca.