Meaning

noun the lowest brass wind instrument

originBorrowed in the 19th century from French tuba (“tuba”), German Tuba (“tuba”), originally Baß-Tuba (literally “bass tuba”), or Italian tuba (“tuba”), from Latin tuba (“tube, trumpet, military trumpet”). The Latin term is of obscure ultimate origin, but is possibly connected to tībia (“shinbone, reed-pipe”); see there.

Etymology from Wiktionary, CC BY-SA 3.0