The word "hypnosis" (from the Greek hypnos, "sleep") is an abbreviation of James Braid's (1841) term "neuro-hypnotism", meaning "sleep of the nervous system".
A person who is hypnotized displays certain unusual characteristics and propensities, compared with a non-hypnotized subject, most notably hyper-suggestibility, which some authorities have considered a sine qua non of hypnosis (although whilst in a trance state patients cannot be made to do anything that is against their moral code).
Clark L. Hull, probably the first major empirical researcher in the field, wrote
If a subject after submitting to the hypnotic procedure shows no genuine increase in susceptibility to any suggestions whatever, there seems no point in calling him hypnotised...
Franz Anton Mesmer held that trance and healing were the result of the channelling of a mysterious "occult" force called "animal magnetism". In the mid-18th Century, this became the basis of a very large and popular school of thought termed "Mesmerism". However, in 1843, the Scottish surgeon James Braid proposed the theory of hypnotism as a radical alternative, in opposition to Mesmerism. Braid argued that the occult qualities of Mesmerism were illusory and that its effects were due to a combination of "nervous fatigue" and verbal suggestion. A bitter war of words developed between Braid and the leading exponents of Mesmerism.
I beg farther to remark, if my theory and pretensions, as to the nature, cause, and extent of the phenomena of nervous sleep [i.e., hypnotism] have none of the fascinations of the transcendental to captivate the lovers of the marvellous, the credulous and enthusiastic, which the pretensions and alleged occult agency of the mesmerists have, still I hope my views will not be the less acceptable to honest and sober-minded men, because they are all level to our comprehension, and reconcilable with well-known physiological