1860, "disease characterized by tubercules," a medical Latin hybrid, from Latin tuberculum "small swelling, pimple," diminutive of tuber "lump" (from PIE root *teue- "to swell") + -osis, a suffix of Greek origin. So called in reference to the tubercules which form in the lungs. Originally in reference to any disease characterized by tubercules; since the discovery in 1882 of the tubercule bacillus by German bacteriologist Robert Koch (1843-1910) restricted to disease caused by this. Abbreviation T.B. attested from 1912.