The word 'Zen' is the Indian word 'Dhyanam'; which is a practical method of self realization. Self realization is the science that India gifted to the world nearly 10,000 years ago.
From the philosophy of Raja Yoga arose the teachings of the Buddha [400~600B.C.]
Around 200A.D. Buddhism was introduced to China and mixed well with Taoism and both prospered. While Buddhism had both ritualizm and meditation, similar to the Brahministic Hinduism in India, gradually the meditation aspect got separated from Buddhism and became an independent science and was called 'Zen' [India: Dhyanam].