According to Wikipedia: "The Shang You or SY-series (Literally "Upstream"), and the Hai Ying or HY-series (Literally "Sea Eagle") were early Chinese anti-ship missiles. They were derived from the Soviet P-15 Termit missile.
The HY-1 and HY-2 received the NATO reporting name Silkworm. However, to confuse matters, Western media also referred to the SY-series, and its export derivatives, the Fei Long or FL-series (Literally "Flying Dragon"), as Silkworms."