Meaning

noun backache affecting the lumbar region or lower back; can be caused by muscle strain or arthritis or vascular insufficiency or a ruptured intervertebral disc

originThe noun is borrowed from Late Latin lumbāgō (“backache of the lumbar region”), from Late Latin lumbus (“lumbar”), Latin lumbus (“loin”) (ultimately from Proto-Indo-European *lendʰ- (“loins”)) + -āgō (suffix forming nouns describing objects, animals, and plants). The verb is derived from the noun.

Etymology from Wiktionary, CC BY-SA 3.0