Cathay is a Elizabethan English name for China.

The ancient Romans called China SERICA. Their knowledge of Asian geography was sketchy. They knew Ceylon/Sri Lanka was an island that was the source of their peppercorns. They called it Taprobane. And its ruler made a state visit to Rome in the time of Augustus, complete with elephants ferried across the Indian ocean to Red Sea ports of Egypt.

But beyond Taprobane, all they knew was that silk came from SERICA.

By the 1200's, there was a thriving trade port of SATIN on the south coast of China, with thousands of Arab traders and a few hundred Europeans as well (mostly Venetian and Byzantine). From this port, comes our name for satin.

By the 1500's, the name Cathay came into widespread use.