Jean Riolan the Younger
Anthropographia et Osteologia. Omnia recognita, triplo auctiora, & emendatoria, ex propriis, ac novis cogitationibus & observationibus, etc. Commentarius didactibus in librum Galeni de Ossibus. Commentorius in Caput XI. De Coccyge. Caput XVIII
Frankfurt: Bryan, 1626: 851-852.
PDF of the page
This page is in a section of the book on anatomy, and does not appear to contain any information about coccydynia.
Sugar translated the first few sentences:
At the end of the sacred bone there is added on a small bone, which by its resemblance to the beak of the cuckoo bird, is called Coccyx; or perhaps from the sound of the noise made when flatulence comes out of the anus instead of out of the mouth, resembling the voice of the cuckoo. Or because such a bone is made to be stuck on to the sacred bone [os sacrum], which they call Kolladon, Kollex, and Kollon, and from this there is derived coccyx, which is in fact called the bone of the colon, and which is cut off and mutilated by the Meletio. It supports the levator ani muscle and the straight intestine [rectum] in order to maintain the fullness of the buttocks projecting beyond the pelvis, and blocking the opening at the end of the spine, protects the spinal medulla from injurious vapors. Finally, by gently taking up blows and bruises, it brings about that fracture will not involve the bone [sacrum]. It [the coccyx] grows or is formed from three or four little bones.
I am as yet unable to determine the background for this legend. Meles or Meletis refers to a river in Ionia near Smyrna, where Homer is said to have been born. Melita is the old Latin name for Malta. So we are left with the apparently fanciful comparison of the bird beak and the bone.