lumbo-

The lower back or loin.

Latin lumbus, loin.

Lumbosacral refers to the lumbar and sacral regions, lumbocostal (Latin costa, rib) to the lumbar region and the ribs, lumbodorsal to the lumbar region and the back (these sometimes appear hyphenated); lumbago is pain in the muscles and joints of the lower back; the adjective is lumbar.