Anatomical Bone Names from Common Names

Lumbar spine is only the region of the back low down but doesn't describe the C-spine or thoracic or sacral spine. Accepted medical nomenclature, depending on context, is vertebra(e); vertebral body; vertebral or spinal column (but this is the whole length not an individual bone). The bony parts that protrude form the back are the spinous processes, but they are vertebral extensions and this term is used to precisely locate injuries and such.

The lumbar spine is the lower back, roughly corresponding to where the ribs end but only comprised of 5 vertabrae. It can't be considered the 'backbone' any more than the mandible, zygoma or parietal bones can be called the skull. Lumbar spine vertebrae are identified as L1-L5. Considering there's 12 in the thoracic, 7 in the cervical (2 of which have unique names) and the sacral has 5; you're asking the poor lower back to carry far more than it can be reasonably expected to bear.