Posterior root of posterior femoral cutaneous nerve

The posterior cutaneous nerve of the thigh (also called the posterior femoral cutaneous nerve) is a sensory nerve of the thigh. It is a branch of the sacral plexus. It supplies the skin of the posterior surface of the thigh, leg, buttock, and also the perineum. Unlike most nerves termed "cutaneous" which are subcutaneous, only the terminal branches of this nerve pass into subcutaneous tissue before being distributed to the skin, with most of the nerve itself situated deep to the deep fascia. (Wikipedia)