Language evolves over time to fit the needs of the culture that speaks it. Every time a new idea or concept enters that culture the language changes to embrace it. As time progresses old ideas might fall by the wayside, and the words once used to describe them find new or different meanings. Tracing the definitions and meanings over the years as they spread from one culture to another is a bit like examining the fossil record, showing the full development of a word from what it is today to what it was hundreds of years ago.
That is what it's like trying to track down the meaning and evolution of the word witch.
If you're looking for an explanation on the biblical mistranslation "Thou shalt not suffer a witch to live" just click the link.
Witch's Modern History
The "Craft of the Wise" Meaning
One of the modern assumptions we have about the word witch is that it refers to a wise one ("the ones with the wits" to quote The Halloween Tree). This definition has seen wide acceptance by the neo-pagan movement, and it has been attributed to Gerald Gardner when he was helping create what would become the Wiccan faith. The person who was actually responsible for this definition is Hugh Ross Williamson, who gave us this explanation in his book The Arrow and The Sword which was published in 1947.
This has been one of the most accepted definitions of what witches are, but there's more to this word than a simple summary. Especially when you do a little bit of additional digging...
Wicca, Wicce, Wiccian
The Old English Stage
One theory takes witch back to Old English where the word wiccian (a verb meaning "to practice witchcraft") is seen as the root. Wiccian was divided by gender into wicca (for male practitioners of the art) and wicce (for women who practiced). Old English as a language was very specific about which words referred to what kind of magic, and scholars believe there were a variety of terms used to describe practitioners of very specific arts. The three words here go back at least to the year 900, and they form a definite bridge with modern witches in terms of the whole "those with wisdom" argument.
The Indo-European Stage
Not all scholars are convinced that the witch-wicca link is as far back as the timeline goes. Professor Jeffrey Russell included an appendix in his book A History of Witchcraft that tied witch to the older Indo-European word weik. This term is similar to the Proto German term wikkjaz (which means necromancer, or "waker of the dead") and the Old Norse term vikja, both of which have figured into the history of witch. According to Russell weik has a general connection to the spiritual and magical, and it is the parent of the word wikk which specifically refers to magic as a force. According to Russel it is weik that represents the ancient starting point of the term.
Why Does Any Of That Matter?
Words have meaning, and when that meaning changes the words take on different aspects. Weikk and wikk were words that likely had spiritual connotations to them. They marked out activities and rituals, as well as people who performed those rituals. The word spread across the continent, influencing societies and languages all across mainland Europe and up into Scandinavia. The word migrated to England, where it laid the groundwork for wicca. By the 1300s or so words like wicca and warlock (more on what is a warlock right here) had taken on very definite devil-worshipy connotations. Those connotations remained for years, until (it could be argued) the more spiritual definition came to the surface once more.
Knowing all of that makes witches more than long-nosed crones with black cats and flying brooms, don't you think?