Originally Posted by Dastan McKay
While you are right that historically there are no evidence of swords on back, it is neither impossible, nor fully impractical.
Here is a video that shows that modified scabbard can allow this, and why whould you want to do this.

But I shure think that rapiers, axes and maces have no place on your back.

dang beaten to the punch.

Shad is great. He also says that with some practice it becomes easier and considering our characters are in fantasy world where sword fighting is very present them practicing with grabbing it from their back doesent sound like a far fetched thought!