The occipital nerve is a main branch of C2 (the second cervical nerve.) C2 exits the spine and travels through the trapezius (upper shoulder muscle connected to the neck) before branching into the greater and lesser occipital nerves. If C2 is compressed or pulled by the trapezius due to arm movements, occipital pain CAN occur. It happened regularly to me in the early stages of my ON, and still happens often.