Lumbago

·noun A rheumatic pain in the loins and the small of the back.

lumbago
lumbāgo, ĭnis, f. [lumbus], lumbago : vitium et debilitas lumborum, Paul. ex Fest. p. 120 Müll. ...

A New Latin Dictionary by Charlton T. Lewis Ph.D. and Charles Short, LL. D.