Did Baum invent his method for killing witches?

Question

The Wicked Witch of the West is killed when water is poured on her head.

I don't remember any other fairy tales where this happens. Did Baum invent this method for killing witches?

Richard provided/found the clip/quote:

". . . the Witch began to shrink and fall away. "See what you have done!" she screamed. "In a minute I shall melt away."

"I am very sorry, indeed," said Dorothy, who was truly frightened to see the Witch actually melting away like brown sugar before her eyes.

"Didn't you know water would be the end of me?" asked the Witch, in a wailing, despairing voice.

"Of course not," answered Dorothy; "how should I?""

I'm melting, I'm melting! Oh what a world!

Apparently Dorothy didn't know about it, but did the world know about it?

Answer 1

The idea that water is proof against supernatural evil is has quite a long pedigree:

• In folklore, vampires sometimes are thought to be unable to cross running water. For example, Dracula cannot do so:

"Thus, whereas he can do as he will within his limit, when he have his earth-home, his coffin-home, his hell-home, the place unhallowed, as we saw when he went to the grave of the suicide at Whitby, still at other time he can only change when the time come. It is said, too, that he can only pass running water at the slack or the flood of the tide."

• Witches, demons and ghosts could not cross water, which Tam O'Shanter took advantage of.
• The Nucklavee fears water.

Especially with regard to witches

And most relevant of all:

• Water was often held to be inimical to witches, such that it could be used as a test to determine whether an accused individual consorted with the Devil. In the Book of James, or Daemonologie, we have the following quote:

The other is their fleeting on the water: for as in a secret murther, if the deade carcase be at any time thereafter handled by the murtherer, it wil gush out of bloud, as if the blud wer crying to the heaven for revenge of the murtherer, God having appoynted that secret super-naturall signe, for tryall of that secrete unnaturall crime, so it appeares that God hath appoynted (for a super-naturall signe of the monstruous impietie of the Witches) that the water shal refuse to receive them in her bosom, that have shaken off them the sacred Water of Baptisme, and wilfullie refused the benefite thereof: No not so much as their eye are able to shed teares (thretten and torture them as ye please) while first they repent (God not permitting them to dissemble their obstinacie in so horrible a crime) albeit the women kinde especially, be able other-waies to shed teares at every light occasion when they will, yea, although it were dissemblingly like the Crocodiles.

Note that the idea that the very tears of the witches have dried up seems extraordinarily similar to Baum's assertion that the Wicked Witch "was so wicked that the blood in her had dried up many years before."