It is an error to say that the Witches in _Macbeth_ "are never called witches" (compare Act i, scene 3: "'Give me!' quoth I. 'A-roint thee, _witch_!' the rump-fed ronyon cries"). However, their designation as Weird Sisters fully settles the case of their Germanic origin.
This name "Weird" is derived from the Anglo-Saxon Norn Wyrd (Sax. _Wurth_; O.H. Ger. _Wurd_; Norse, _Urd_), who represents the Past, as her very name shows. Wurd is _die Gewordene_--the "Has Been," or rather the "Has Become," if one could say so in English.
In Shakspeare the Witches are three in number--even as in Norse, German, as well as in Keltic and other mythologies. Urd, properly speaking, is the Past. Skuld is the Future, or "That Which shall Be." Verdandi, usually translated as the Present, has an even deeper meaning. Her name is not to be derived from _vera_ (to be), but from _verda_ (Ger. _werden_). This verb, which has a mixed meaning of "to be," "to become," or to "grow," has been lost in English. Verdandi is, therefore, not merely a representative of present Being, but of the process of Growing, or of Evolution--which gives her figure a profounder aspect. Indeed, there is generally more significance in mythological tales than those imagine who look upon them chiefly as a barren play of fancy.
Incidentally it may be remarked that, though Shakspeare's Weird Sisters are three in number--corresponding to Urd, Verdandi and Skuld--German and Northern mythology and folk-lore occasionally speak of twelve or seven of them. In the German tale of _Dornröschen_, or the Sleeping Beauty, there are twelve good fays; and a thirteenth, who works the evil spell. Once, in German folk-lore, we meet with but two Sisters of Fate--one of them called _Kann_, the other _Muss_. Perhaps these are representatives of man's measure of free will (that which he "can"), and of that which is his inevitable fate--or, that which he "must" do.
Though the word "Norn" has been lost in England and Germany, it is possibly preserved in a German folk-lore ditty, which speaks of three Sisters of Fate as "Nuns." Altogether, German folk-lore is still full of rimes about three Weird Sisters. They are sometimes called Wild Women, or Wise Women, or the Measurers (_Metten_)--namely, of Fate; or, euphemistically, like the Eumenides, the Advisers of Welfare (_Heil-Räthinnen_), reminding us of the counsels given to Macbeth in the apparition scene; or the Quick Judges (_Gach-Schepfen_). Even as in the Edda, these German fays weave and twist threads or ropes, and attach them to distant parts, thus fixing the weft of Fate. One of these fays is sometimes called Held, and described as black, or as half dark half white--like Hel, the Mistress of the Nether World. That German fay is also called Rachel, clearly a contraction of Rach-Hel, i.e. the Avengeress Hel.