You know that saying that originated with werewolves – everyone has their silver bullet, like an Achilles heel? Werewolves didn’t have their silver bullet. In fact, they had absolutely nothing. All of that comes from later popular culture. Specifically, it was popluarlized (but did not exclusively originate in) the The Wolf Man (1941) movie and its writer, Curt Siodmak.
There’s not a scrap of folkloric roots in the idea that only silver can kill a werewolf, because werewolves had no catchall weaknesses, and they certainly had no problem with silver.
Yes, there were other stories before Siodmak’s work that mention silver in relation to slaying werewolves. Were they stories from folklore, or were they always written as fiction? The latter seems to be largely true.
There were ways to potentially defeat werewolves or force them to turn back into a human, but there wasn’t any catchall silver, holy artifact, or belladonna to drive them off. Werewolves could walk holy ground, wave as many crucifixes around as they pleased, and take a bath in holy water, despite some people today tacking modern vampire weaknesses (in itself a long subject) onto them. Wolfsbane and belladonna are also modern contrivances. By and large, actually killing a werewolf (especially if they were in their werewolf form) was very, very hard, and sometimes impossible.
There’s some debate among werewolf scholars about this silver issue. Not a lot, but some. Because, at one point in the history of werewolf studies, a few people started circulating this idea that the Beast of Gevaudan (an unknown creature that killed many people in France from approximately 1764 to 1767) was killed by a silver bullet. This idea was contrived by a writer and then werewolf scholars latched onto it so hard that some of them started thinking it was actually a part of the old accounts. Specifically, the idea that the Beast was slain with a silver bullet comes from a novel published in 1946: Henri Pourrat’s Historie fidèle de la bête en Gévaudan.
When it comes to modern werewolf concepts, though, basically just look to The Wolf Man and, to some degree, its sequels and spinoffs. It popularized everything we know today. Curt Siodmak singlehandedly dictated to the world what werewolves are and are supposed to be. This definitely isn’t the last time you’ll be hearing about that movie and how, for good or for ill, it’s where the werewolves of today originated.
If I had to guess? Siodmak decided to use the silver thing because many sources claim that silver is, alchemically, associated with the moon, and he definitely went the moon route with his werewolves. Or perhaps it came from another thing…
Not only did Curt Siodmak and many other works of assorted time periods even ranging back to the 1600s apply it to werewolves, but the idea of werewolves being weak to/only able to be slain by silver has retroactively been applied to werewolves in scholarship more often because of scholars broadening the range of what is and isn’t a werewolf legend – and having those legends also include witches.
And, of course, this is partially a result of silver being applied to werewolves in pop culture – scholarships look for it in folklore, when it isn’t there, and try to apply it, and it doesn’t work.
Which is, of course, ridiculous. Werewolf legends and witch legends are two entirely different things.
In some legends, especially as sourced by Montague Summers (who was a foremost scholar on witches, vampires, and, to some degree, werewolves), witches and “witch-creatures” (witches turned into animals) were weak to silver and could be slain by silver. This didn’t have any association with werewolves or wolves, though – those witches could have been turned into a hare, a cat, a wolf, a dog… witches turned into basically everything.
But witches, unlike werewolves, did not have a tail in their animal forms, and this was the primary means through which you could tell the difference between something like a witch or a werewolf.
So the point is…
Witches are not werewolves. The mythology and folklore behind them are extremely different, and I think it’s very wrong and frankly stupid of scholars to ever try equating the two. It creates festering confusion and also muddies the definition of what is and isn’t a werewolf legend – something very important in scholarship.
That, and stories of witches as opposed to werewolves are so radically different that it has, to some degree, also caused other, more negative things to be applied to werewolves in popular culture, because they were concepts taken from witch legends instead. And that bothers me.
So yeah – while I think that werewolves being weak to/sensitive to/only be killable by silver can be really fun, when done properly, it is still not a part of historical werewolf mythology/folklore. The concept almost certainly was carried over by writers from witch stories.