Online Etymology Dictionary

occultism: 1881, from occult + -ism.
occultation: mid-15c., from L. occultationem, noun of action from occultare, from occultus (see occult).
occult: 1530s, "secret, not divulged," from L. occultus "hidden, concealed, secret," pp. of occulere "cover over, conceal," from ob "over" + a verb related to celare "to hide," from PIE base *kel- (see cell). Meaning "not apprehended by the mind, beyond the range of understanding" is from 1540s. The association with the supernatural sciences (magic, alchemy, astrology, etc.) dates from 1630s.
elemental (adj.): late 15c., “pertaining to the four elements,” from M.L. elementalis, from L. elementum (see element). Meaning “simple, uncomplicated” is from 1550s; that of “relating to first principles” is from 1570s. The noun in the occult sense is from 1877.
cryptic: 1630s, "hidden, occult, mystical," from L.L. crypticus, from Gk. kryptikos "fit for concealing," from kryptos "hidden" (see crypt). Meaning "mysterious, enigmatic" is recorded from 1920. Related: Cryptically.
numerology: 1911, "study of the occult meaning of numbers," a hybrid from L. numerus "number" + Gk. -logia, from logos "one who speaks (of a certain topic)." A correct formation would be arithmology, from Gk. arithmos "number."
glamor: also glamour, 1720, "magic, enchantment" (especially in phrase to cast the glamor), a variant of Scot. gramarye "magic, enchantment, spell," alteration of English grammar (q.v.) with a medieval sense of "any sort of scholarship, especially occult learning." Popularized by the writings of Sir Walter Scott (1771-1832). Sense of "magical beauty, alluring charm" first recorded 1840.
influenza: 1743, borrowed during an outbreak of the disease in Europe, from It. influenza "influenza, epidemic," originally "visitation, influence (of the stars)," from M.L. influentia (see influence). Used in It. for diseases since at least 1504 (cf. influenza di febbre scarlattina "scarlet fever") on notion of astral or occult influence. The 1743 outbreak began in Italy. Often applied since mid-19c. to severe colds.
hermetic: c.1600 (implied in hermetically), "completely sealed," also (1630s) "dealing with occult science or alchemy," from L. hermeticus, from Gk. Hermes, god of science and art, among other things, identified by Neoplatonists, mystics, and alchemists with the Egyptian god Thoth as Hermes Trismegistos "Thrice-Great Hermes," who supposedly invented the process of making a glass tube airtight (a process in alchemy) using a secret seal.
Wicca: An O.E. masc. noun meaning "male witch, wizard, soothsayer, sorcerer, magician;" see witch. Use of the word in modern contexts traces to English folklorist Gerald Gardner (1884-1964), who is said to have joined circa 1939 an occult group in New Forest, Hampshire, England, for which he claimed an unbroken tradition to medieval times. Gardner seems to have first used it in print in 1954, in his book "Witchcraft Today" (e.g.: "Witches were the Wica or wise people, with herbal knowledge and a working occult teaching usually used for good ...."). In published and unpublished material, he apparently only ever used the word as a mass noun referring to adherents of the practice and not as the name of the practice itself. Some of his followers continue to use it in this sense. According to Gardner's book "The Meaning of Witchcraft" (1959), the word, as used in the initiation ceremony, played a key role in his experience:
I realised that I had stumbled upon something interesting; but I was half-initiated before the word, 'Wica' which they used hit me like a thunderbolt, and I knew where I was, and that the Old Religion still existed. And so I found myself in the Circle, and there took the usual oath of secrecy, which bound me not to reveal certain things.
In the late 1960s the term came into use as the title of a modern pagan movement associated with witchcraft. The first printed reference in this usage seems to be 1969, in "The Truth About Witchcraft" by freelance author Hans Holzer:
If the practice of the Old Religion, which is also called Wicca (Craft of the Wise), and thence, witchcraft, is a reputable and useful cult, then it is worthy of public interest.
And, quoting witch Alex Sanders:
"No, a witch wedding still needs a civil ceremony to make it legal. Wicca itself as a religion is not registered yet. But it is about time somebody registered it, I think. I've done all I can to call attention to our religion."
Sanders was a highly visible representative of neo-pagan Witchcraft in the late 1960s and early 1970s. During this time he appears to have popularized use of the term in this sense. Later books c.1989 teaching modernized witchcraft using the same term account for its rise and popularity, especially in U.S.
sigil: “sign,” c.1600, from L.L. sigillum, from L. sigilla (neut. pl.), dim. of signum “sign” (see sign (n.)). In astrology, an occult device supposed to have great power (1650s).
When my mistress died, she had under her arm-hole a small scarlet bag full of many things, which, one that was there delivered unto me. There was in this bag several sigils, some of Jupiter in Trine, others of the nature of Venus, some of iron, and one of gold, of pure angel-gold, of the bigness of a thirty-three shilling piece of King James's coin. ["The Antiquarian Repertory," London, 1780]
mystic (adj.): late 14c., "spiritually allegorical, pertaining to mysteries of faith," from O.Fr. mistique, from L. mysticus, from Gk. mystikos "secret, mystic," from mystes "one who has been initiated" (see mystery (1)). Meaning "pertaining to occult practices or ancient religions" first recorded 1610s. The noun meaning "exponent of mystical theology" is from 1670s, from the adjective. The place name in Connecticut is deformed from Algonquian missituk "great tidal river," from missi "large" + -tuk "tidal river."
astrology: late 14c., from L. astrologia "astronomy," from Gk. astrologia "telling of the stars," from astron "star" (see astro-) + -logia "treating of" (see -logy). Originally identical with astronomy, it had also a special sense of "practical astronomy, astronomy applied to prediction of events." This was divided into natural astrology "the calculation and foretelling of natural phenomenon" (tides, eclipses, etc.), and judicial astrology "the art of judging occult influences of stars on human affairs" (also known as stromancy, 1650s). Differentiation between astrology and astronomy began late 1400s and by 17c. this word was limited to "reading influences of the stars and their effects on human destiny." Astrological is recorded from 1590s.
gas: 1658, from Du. gas, probably from Gk. khaos "empty space" (see chaos). The sound of Du. "g" is roughly equivalent to that of Gk. "kh." First used by Flem. chemist J.B. van Helmont (1577-1644), probably influenced by Paracelsus, who used khaos in occult sense of "proper elements of spirits" or "ultra-rarified water," which was van Helmont's definition of gas. Modern scientific sense began 1779, focused on "combustible mix of vapors" (1794, originally coal gas); "anesthetic" (1894, originally nitrous oxide); and "poison gas" (1900). Meaning "intestinal vapors" is from 1882. Slang sense of "empty talk" is from 1847; slang meaning "something exciting or excellent" first attested 1953, from earlier hepster slang gasser in the same sense (1944). Gas also meant "fun, a joke" in Anglo-Irish and was used so by Joyce (1914). As short for gasoline (q.v.), it is Amer.Eng., first recorded 1905.
grammar: late 12c., gramarye, from O.Fr. grammaire "learning," especially Latin and philology, from L. grammatica, from Gk. grammatike tekhne "art of letters," with a sense of both philology and literature in the broadest sense, from gramma "letter," from stem of graphein "to draw or write" (see -graphy). Restriction to "rules of language" is a post-classical development, but as this type of study was until 16c. limited to Latin, M.E. gramarye also came to mean "learning in general, knowledge peculiar to the learned classes" (early 14c.), which included astrology and magic; hence the secondary meaning of "occult knowledge" (late 15c.), which evolved in Scottish into glamor (q.v.). A grammar school (late 14c.) was originally "a school in which the learned languages are grammatically taught" [Johnson, who also has grammaticaster "a mean verbal pedant"]. In U.S. (1860) the term was put to use in the graded system for "a school between primary and secondary, where English grammar is taught."