Note: Sybil is also spelled sibyl. All of the links I used in my research described "sybil", so I opt for sybil--an unresolvable issue of transliteration. A quality node at Sibyl deals with TS Eliot's treatment of the legend.
- Sybil was a Phrygian godess often associated with the Roman Demeter or Rhea. She was the godess of fertility and healing, almost always appearing in a crown, and attended by lions. She is associated with the wild, with fecundity and nature.
- A "sybil" is a word for any of a number of prophetess-seers, at the oracle of Delphi and elsewhere. Sybils were said to be able to predict the future and/or relay messages from the gods. It was a sybil in Virgil's Aeneid that led Aeneas into the cave and down to Hades and the river Styx. A somewhat more modern reference to a sybil is made in Eliot's The Wasteland. These sybils often spoke in riddles, and there is even said to have been one at Cumae who would write her prophesies on leaves and then "scatter them in the wind".
- Sybils also appear in Norse mythology, most notably in creation lore. "The Song of the Sybil" is one of the earliest documents written on Norse mythology; the narrator is a sybil, and she declares the existence of the 9 worlds, and she recounts a colorful yet solemn history of giants and dwarves and war. The final three stanzas:
Fairer than sunlight,
I see a hall
A hall thatched with gold
in Gimle:
Kind Lords
shall live there
in delight
for ever.
Now rides the Strong One
to Rainbow Door,
Powerful from heaven,
the All-Ruler.
From the depths below
a drake comes flying
The dark dragon
from Darkfell,
Bears on his pinions
the bodies of men,
Nidhogg is near.
Soars overhead I sink now.
- Hildegard von Bingen (1098-1179) was known as the "Sybil of the Rhine". She was a reknowned theologian and "visionary" writer, and she was an esteemed composer; she also served in an advisory capacity to many high-ranking church officials, and both the pope and king--it was this aspect of her seer-like intellect that qualified her as a "sybil".
http://www.uh.edu/engines/epi1198.htm
http://www.dreamwater.net/padfoot/Analysis/Names.html
http://www.fva.is/~harpa/comenius/it_sybil.html
http://www.heathenry.org/lore/poetic_edda/voluspa_f.html
http://www.heathenry.org/heidnibok/poetic_edda.html
http://www.fordham.edu/halsall/med/hildegarde.html | 
