Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Essential Tremor ?
    ### Response:
    Tremor is an unintentional, somewhat rhythmic, muscle movement involving to-and-fro movements (oscillations) of one or more parts of the body. Essential tremor (previously called benign essential tremor) is the most common form of abnormal tremor. (In some people, tremor is a symptom of a neurological disorder or appears as a side effect of certain drugs.
    