In other cases the pain appears to be neuralgic in character, and is referable to the fifth sacral and the coccygeal nerves, or to the terminal branches of the sacral plexus distributed in this region.
"Manual of Surgery Volume Second: Extremities--Head--Neck. Sixth Edition."
Alexander Miles Alexis Thomson
They are: the ischio-coccygeal, superior sacro-coccygeal, lateral sacro-coccygeal, and inferior sacro-coccygeal.
"Artistic Anatomy of Animals"
Édouard Cuyer
In the pig, it also takes origin higher up from the sacro-sciatic ligament and the coccygeal aponeurosis.
"Artistic Anatomy of Animals"
Édouard Cuyer