I have played Ocarina of Time and Majora's Mask and I am always asking: "What is this thing on Link's back?" It's for putting the sword, I know that, but what it's called? I have searched for "sword quiver" and it only showed quivers. So, what is it called?
It's called a scabbard or sheath:
a long, thin cover for the blade of a sword, usually attached to a belt
Scabbard is the more specific word used, Where sheath is used more generally.
Definition: a holder for a bladed weapon such as a sword or bayonet; sheath.
Definition: something that surrounds and protects another thing.
Sheath refers to a outer casing on multiple different things. A scabbard is a type of sheath specifically for swords, blades, or guns.
From Wikipedia, the free encyclopedia
Sheath may refer to:
Scabbard, a sheath for holding a sword, knife, or other large blade, as well as guns, such as rifles.
The outer covering of a cable.
Condom, a kind of contraception.