Sword Breaker.

Humm.

On its own this isn't much of a myth in so far as there isn't much to test. However it might work as part of a 'sword-myths' segment or episode, especially if they are historical in nature.

Or it could be someone just misspelled/misinterpreted it and it would be better called a sword brake?

Wow... I had almost forgotten this one.
And forgotten to come back "As well"...
Can I update with something I found since, in that if you twist sideways, you can get a hell of a grip on the sword trapped, and a quick flick of the wrist and a hell of a heave, you can wrench the sword out of the hand of the opponent.
Or enough to unbalance them if they have a good grip, then release their sword and bring your own to bear on their unprotected backside?..

In some films you sometimes see a sword used as a thrown weapon, I wonder how good one would actually be in real life?

Thinking on swords I wonder if the myth of tempering and quenching a blade in different substances would be testable? Or of any interest?

Take a billet of steel and createn several different identical lengths of steel and temper and quench them in water, oil animal blood, urine etc. I am sure several good historical and mythological stories of smiths using certain substances can be found.
Then do testing on each to see how the steel performs after quenching.

Before they knew about such things as steel, Iron swords, quench in water, you have just iron.
Quench in Blood, which contains carbon, you have a "basic" form of steel with the transfer of carbon to the iron.
Dont know how much or how accurate that is, but its what I have been told by re-enactment archaeology by guys using those old methods for creating sword blades.
Also on that, the making of a blade, and fool can bash a sword shape, but using the pre-enlightemnent version of "Standards" way of making a sword when it was a skilled sword smithy doing an almost ceremonial handed down way of making a sword, you take much more care when doing that, so perhaps that has something to do with it?.. if it works and makes a better blade, you do it again next time.
Perhaps then also use a basic bash it into shape method of creating a blade against a skilled sword smith.

Please excuse my newness, there is a learning curve on my part.
I know this is an old subject from early 2017.
I don't blacksmith but I went to vocational college in the early & mid 1980's for both welding and tool & die which both had different degrees of metallurgy.
I had worked making bandsaw blades & had 3 different lengths of heat treat ovens that were the final stages before both ends of 1200ft were tested for hardness, Brinell or Rockwell & their tolerances that are all but forgotten. Since the 0.0200 by .5000 of an inch were milled 8 inches at a time & up to 80 could of 0.0200 of an inch high cabin and/or bimetal stock. We also had up to 3 streams of oil that were applied just before the exit of the heat treater.
All this with endless testing, measuring & adjustments.
I was asked to test & record different quenching mediums but only for the sake of curiosity. On thing got their attention, though it wasn't consistent because of the application. This was Ivory soap, I tried it because my dad told me that he heated up cheap knife blades that weren't stainless steel of course.
This reminds me of a TV program years ago that shown how a type of clay was applied to the back of samurai swords & leaving maybe 3/4 of an inch of the sharp side free of this clay.
This leaves the wavy line at center of the blade and only the cutting edge hard enough to keep it sharp alot longer.
The clay covered backbone is softer so the blade is less likely to be broken and the harder side helps keep it from being bent (2 different characteristics or and I will alloys from the same steel). Both parts of the blade help the other and this is how the bandsaw blades were made but without the clay and with a more concentrated flames in the heat treater. The oil was poured on from the top where the teeth are, theory is that the teeth are being heated and cooled more than the opposite side.
As a last recollection, during welding classes we had to go to a closed off area just before being carefully dismantled and sealed somewhere probably for ever. There was this tapped off area with like a witches cauldron in the middle with what looked like a melted overflow of a white mineral caked in a frozen manner down the outside and then teach told us what it was, it was cooled sodium cyanide. They used this in its molten form in the past right there. It got my attention to say the least.
I can only imagine the precautions taken to use this to just quench a little steel and I never looked up the resulting characteristics and what the benefits are. Personally I don't think it would be worth the risks and I think that might be why the college was getting rid of it.
I just thought I'd throw you some knowledge (that you probably already know).
I still do some artistic/utilitarian stick and ac/dc Tig welding as often as can in my garage and some steel annealing and hardening when it comes up, like with some blades and different kinds of brackets.
I was thinking about looking more into trying the Japanese Clay Dam trick.
I think it's really something I'd like to try.
Give me your thoughts and/or your similar knowledge/experiences.

Okay, here is another take on this.

Several years ago, I went to a museum town that recreated a town from the 1830's-1840's. Part of this was the blacksmith. They did a demo talking about working with iron and the process of quenching it. The person doing the demo said that the final step used was to quench hot steel in cow/horse manure. They stated that it would absorb carbon from the excrement which would harden the steel and also provide a coating that would protect against rust.

They then went on to say that for the purposes of the demo, they could not use manure today due to heath codes, but they had found that used motor oil was a perfect substitute, treating the metal in the same way. SO the joke was that today, just like in the 1830's they quench metal in the waste from their mode of transportation.

I have no idea how realistic that is. Is there any truth to this, or is this all bull****? Sorry, this just lead to the perfect pun.

I can tell you for a fact that modern swordsmiths DO quench blades in used motor oil.

to get a little more nuts and bolts - how rapidly the sword is cooled does have an effect on its ratio of hardness to toughness. (remember that too much hardness makes it more likely to shatter and too little makes it more likely to bend) oil cools the steel more slowly than water does. and hence is better for things that need to be tougher. I've also been familiarized with using oil to apply a carbon oxide layer on forged steel - for which nonstick cooking spray is often used on stuff that needs to be all toughness and little hardness. (like, say, decorative wrought iron)