The word [coccyx] is Greek and means "cuckoo". It is the name of the lower segment of the spinal column, and was named by Herophilus of Alexandria (325-255BC) because of a resemblance of this structure to the bill of the cuckoo bird.  Vesalius also used the same analogy. There is another structure of the body named after the beak of a bird, do you know it? If not, click here.

The coccyx (vernacularly known as "tailbone") is usually represented by four rudimentary vertebrae, although the number varies between 3 to 5 vertebrae. There have been reported cases of "human tails" but these do not have a bony structure and are usually related to congenital abnormalities such as spina bifida. 

The coccyx has a well-formed superior component, which usually presents with two cornua (horns) which serve as part of a rudimentary zygapophyseal (facet) joint. The lower coccygeal vertebra is usually a small bony node. 

The coccyx has an anterior sacrococcygeal ligament, which is continued with the anoccygeal raphe, a ligamentous structure that serves as a posterior attachment for muscular components of the pelvic diaphragm, and helps anchor the anal canal. The coccygeus muscle, the posterior component of the pelvic diaphragm and part of the sacrospinous ligament also attach to the anterolateral aspect of the coccyx.

Coccygeal pain is referred to as coccydynia

Coccyx ( courtesy of: