Archeologists surmise that swords were bent like that (this one is in a circle, which is kind of special, but most are just plied in two or three) to 'kill' the sword and thus make it pass into the Otherworld, where it could be used normally. So this sword accompanied its master into death. Often the weapons that are made unusable like this are really fine items and seemingly too fancy for use in real life. Many of them were brandnew too!

[ctd. in my reply to Cecilia below :)]