The prefix double means that the instrument sounds an octave lower than it is written:

True

Explanation:

Violone and Violon da gamba were two instruments also considered the predecessors of the double bass which were introduced to the musical scene just to support the Violoncello which was basically the bass of the strings. And the sounds that were produced were an octave lower than the one written in the notes. However, prefix doubles means the same. It means the produced sound is one octave lower than the noted one.