Nerve, sciatic: The largest nerve in the body, the sciatic nerve begins from nerve roots in the lumbar part of the spinal cord (in the low back) and extends through the buttock area to send nerve endings down to the legs.
Pain resulting from irritation of the sciatic nerve is called sciatica. The pain is typically felt at the back of the thigh. While sciatica is most commonly a result of a disc herniation directly pressing on the nerve, any cause of irritation or inflammation of this nerve can reproduce the symptoms of sciatica.
The name "sciatic" came via Latin from the Greek "ischiadikos" which means "subject to trouble in the hips or loins."