Is it farther or further?
1570s, from Late Latin spinalis, from spina (see spine).
spinal spi·nal (spī'nəl)adj.
Relating to or situated near the spinal column or spinal cord.
Relating to any spine or spinous process.
See vertebral column.
Any of various pointed projections, processes, or appendages of animals.
A sharp-pointed projection on a plant, especially a hard, narrow modified leaf, as on a cactus, that is adapted to reduce water loss. Compare thorn. See more at leaf.