Final answer:
The Italian term for a technique created by a violinist's shaking arm is vibrato, which adds expression and richness to the sound produced by a violin.
Step-by-step explanation:
The Italian term for a technique or effect created by a violinist's shaking arm is vibrato. Vibrato is a musical technique in which the pitch of a note is varied by rapidly and repeatedly altering the tension of the vibrating string with the bowing arm. This technique adds expression and richness to the sound produced by a violin.