Hypnosis as a word is derived from Greek mythology where Hypnos is the personification of sleep. The association between the state of mind we know as hypnosis and the Greek mythology was made by James Braid. He had become interested in the phenomenon of mesmerism, but soon found that the theories of mesmerism weren't believeable. He founded his own theories of hypnosis as a state of focused attention and for these theories not to have any association with the beliefs of people practicing mesmerism, he used the word hypnotism.

In his early studies of what we now know as hypnosis, led him to believe that the state of mind was somehow similar to the sleeping state. He changed his mind about this in later studies, but at that time the terminology he had founded was too strong to change. Although he suggested a different term, hypnotism had caugt on.

So if you are familiar with Greek mythology, you now know why the word hypnosis comes so close to the name of Hypnos. It is important that you understand, that even James Braid who coined the term found out that the state of hypnosis isn't the same as the state of sleep. They can be very similar in the way the subject looks like in the two states, but the internal processes of the subjects mind are quite different. You may even hear hypnotists use the word "sleep" as a command to have the subject enter into the state of hypnosis. Many hypnotists wouldn't mind changing this word, if only they could find a more appropriate one, that both enables the subject to understand the command and clears the misunderstanding of hypnosis as sleep.