I don't speak Biblical Hebrew—no one does any more—but I can read it, and I do speak Israeli Hebrew, which is based on the language of the Tanakh (Hebrew Bible). Here's what I can tell you about Exodus 22:18, that much-vexed Biblical passage about suffering a witch to live.
Like most ancient languages, ancient Hebrew had lots of words for "magic." (Interestingly, the ancients rarely, if ever, had a generic term—like "magic”—to cover them all; apparently they didn't perceive them as belonging to the same category.) In Hebrew, one kind of magic is késhef (kaf-shin-fe, for those of you with a reading knowledge of the alef-beit); a woman who practices keshef magic is a mkhashefá, which in the KJV is rendered "witch." Unfortunately, at this remove of time we simply don't know what made keshef distinctive from other forms of magic. To read it as herb-craft is nothing but a guess, or at best a back-reading from Septuagint Greek pharmakos and Vulgate Latin venefica.
Since a standard definition of "witch" in English is "a woman who practices magic,” personally I would say that rendering mkhashefa as "witch" is actually a pretty fair translation. Why it should surprise anyone that the Tanakh is anti-magic (or anti-witch, by any definition) is what puzzles me.
Re. keshef: Philologist Ernest Klein lists Akkadian kushshupu (which he translates as "to practice sorcery") and kashshapu ("sorcerer") as cognates of the Hebrew term, so clearly the root of the word has something to do with magic. (Historians of the word "witch" will be feeling a sense of déjà-vu right about now.) It's not connected with the root for "whisper" (lamed-het-shin); lákhash is a different kind of magic (one could translate "charm" or "incantation," maybe). I should mention that in Modern Hebrew mkhashefa is a witch pure and simple, pointy black hat and all. Of the Israeli Wiccans in my acquaintance, some use the word, some don't. (BtW, you should hear the "Charge of the Goddess" in Hebrew. Amazing.)
It's interesting that by the time of the Talmud (roughly the 2nd-3rd centuries CE), the rabbis apparently no longer knew what specific kind of magic keshef was. Their discussions of Exodus 22:18 focus on two things. The first is: Why is mkhashefa feminine here? (Most laws are phrased in the generic masculine; one would expect the masculine kasháf instead.) Was keshef a form of magic practiced only (or largely) by women, or is it just that women are more prone to using magic?
The second was the verb, the "suffer to live" part. In Hebrew, a notoriously compact language, the entire phrase is a terse three words: Mkhashefá lo tkhayé (mem-khaf-shin-fe-he lamed-alef tav-het-yod-he). Lo is "no, not." The root of the verb, which is second person masculine singular, is the root meaning "to live", but in the "causative" conjugation. So the literal meaning is: "Do not cause a mkhashefa to live." What the rabbis couldn't decide (both opinions, typically, are preserved in the Talmud) was whether this meant that you should kill her outright or just not help her make a living, i.e. don't patronize her.
For me, I'm with the rabbis here. In my experience, it's never a good idea to patronize a witch.