The name Tromba was first used by Italian organ builders for Trumpet stops. In the 18th century German and English builders began using the name for a chorus reed whose tone was midway between that of the Trumpet and the Tuba: smoother, broader, and less brassy than the Trumpet, but not as powerful as the Tuba. It was favored by Harrison & Harrison for their Great divisions. The name has also been used for an 8' extension of a 16' pedal Trombone. Audsley claims that the name was also used by Spanish and Portuguese builders, but we know of no examples.
Osiris contains about 120 examples, six at 16' pitch, one at 4', one at 64', and the rest at 8'. At least sixteen are known to be 8' extensions of 16' pedal Trombones.