For the edification of inquiring minds:
Etymology
The term coccyx is derived from the ancient Greek word κόκκυξ[17][18] kokkyx "cuckoo";[19] the latter is attested in the writings of the Greek physician Herophilus to denote the end of the vertebral column.[20] This Greek name for the cuckoo was applied as the last three or four bones of the coccyx resemble the beak of this bird,[17][20][21][22] when viewed from the side.[9][23]
This established etymological explanation can also be found in the writings of the 16th century anatomist Andreas Vesalius who wrote: os cuculi, a similitudine rostri cuculi avis [20] (the cuckoo bone shows a likeness to the beak of the cuckoo bird). Vesalius used the Latin expression os cuculi, with os, bone[24] and cuculus, the Latin name for the cuckoo.[24] The 16th/17th century French anatomist Jean Riolan the Younger gives a rather hilarious etymological explanation, as he writes: quia crepitus, qui per sedimentum exeunt, ad is os allisi, cuculi vocis similitudinem effingunt [20] (because the sound of the farts that leave the anus and dash against this bone, shows a likeness to the call of the cuckoo). The latter is not considered as potential candidate.[20][21]
Besides os cuculi, os caudae,[20][25] with caudae, of the tail[24] is attested. This Latin expression might be the source of the English, French language, German and Dutch terms tailbone, l'os de la queue,[25] Schwanzbein [21][25] and staartbeen.[26] In the current official anatomic Latin nomenclature, Terminologia Anatomica,[27] coccyx and os coccygis is used.
