Shakespeare's witches are prophets who hail Macbeth, the general, early in the play, and predict his ascent to kingship. Upon killing the king and gaining the throne of Scotland, Macbeth hears them ambiguously predict his eventual downfall. The witches, and their "filthy" trappings and supernatural activities, all set an ominous tone for the play.
Artists in the eighteenth century (e.g., Henry Fuseli, William Rimmer) depicted the witches variously, as have many directors since. Some have exaggerated or sensationalised the hags, or have adapted them to different cultures, as in Orson Welles's rendition of the weird sisters as voodoo priestesses. Some film adaptations have cast the witches as such modern analogues as hippies on drugs, or goth schoolgirls. Their influence reaches the literary realm as well in such works as the Discworld and Harry Potter series.
The name "weird sisters" is found in most modern editions of Macbeth. However, the First Folio's text reads:
In later scenes in the first folio the witches are called "weyward", but never "weird". The modern appellation "weird sisters" derives from Holinshed's original Chronicles. However, modern English spelling was only starting to become fixed by Shakespeare's time and also the word 'weird' (from Old English wyrd, fate) had connotations beyond the common modern meaning. The Wiktionary etymology for "weird" includes this observation: " was extinct by the 16th century in English. It survived in Scots, whence Shakespeare borrowed it in naming the Weird Sisters, reintroducing it to English. The senses "abnormal", "strange" etc. arose via reinterpretation of "Weird Sisters" and date from after this reintroduction."
One of Shakespeare's principal sources for the Three Witches is found in the account of King Duncan in Raphael Holinshed's history of Britain, The Chronicles of England, Scotland, and Ireland (1587). In Holinshed, the future King Macbeth of Scotland and his companion Banquo encounter "three women in strange and wild apparell, resembling creatures of elder world" who hail the men with glowing prophecies and then vanish "immediately out of their sight". Holinshed observes that "the common opinion was that these women were either the Weird Sisters, that is… the goddesses of destiny, or else some nymphs or fairies endued with knowledge of prophecy by their necromantical science"