the cocyx is the tailbone
Possibly a swollen lymph node
The correct spelling of the bone is the coccyx (tail bone, lowest bone on the spine for tailless primates).
If you mean the tailbone, it is called the coccyx.
The inferior most tip of the vertebral column is the coccyx, also known as the tailbone. It is made up of four small vertebrae that are fused together. The coccyx serves as an attachment point for various muscles, tendons, and ligaments.