(Sanskrit योग) “union.” Similar to the Latin “religare,” the root of the word “religion.” In Tibetan, it is “rnal-‘byor” which means “union with the fundamental nature of reality.”
“The word YOGA comes from the root Yuj which means to join, and in its spiritual sense, it is that process by which the human spirit is brought into near and conscious communion with, or is merged in, the Divine Spirit, according as the nature of the human spirit is held to be separate from (Dvaita, Visishtadvaita) or one with (Advaita) the Divine Spirit.” – Swami Sivananda, Kundalini Yoga