Zen is a school of Buddhism which originated in China during the 7th century, and spread to Vietnam, Korea, and Japan. It emphasises rigorous meditation practices, and favours direct personal understanding rather than knowledge of doctrine.
Zen meditation became known in the West at the end of the 19th century, and at this time it became used as an English name, albeit sporadically. Interest in the practice and philosophy of Zen grew during the 1950s and '60s, though the name's usage remained sporadic and it wasn't until the late 1990s and 2000s that this name began to be used more frequently.