mid-14c. (implied in Tartary, "the land of the Tartars"), from Medieval Latin Tartarus, from Persian Tatar, first used 13c. in reference to the hordes of Ghengis Khan (1202-1227), said to be ultimately from Tata, a name of the Mongols for themselves. Form in European languages probably influenced by Latin Tartarus "hell" (e.g. letter of St. Louis of France, 1270: "In the present danger of the Tartars either we shall push them back into the Tartarus whence they are come, or they will bring us all into heaven").
The historical word for what now are called in ethnological works Tatars. A Turkic people, their native region was east of the Caspian Sea. Ghengis' horde was a mix of Tatars, Mongols, Turks, etc. Used figuratively for "savage, rough, irascible person" (1660s). To catch a Tartar "get hold of what cannot be controlled" is recorded from 1660s; original sense not preserved, but probably from some military story similar to the old battlefield joke:
Irish soldier (shouting from within the brush): I've captured one of the enemy.
Captain: Excellent! Bring him here.
Soldier: He won't come.
Captain: Well, then, you come here.
Soldier: I would, but he won't let me.
Among the adjectival forms that have been used are Tartarian (16c.), Tartarous (Ben Jonson), Tartarean (17c.); Byron's Tartarly (1821) is a nonce-word (but a good one). Tartar sauce is attested by 1855, from French sauce tartare.
An Old English masc. noun meaning "male witch, wizard, soothsayer, sorcerer, astrologer, 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" ("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 In published and unpublished material, he apparently only ever used the word as a mass noun referring to adherents of the practice and not as the name of the practice itself.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.