How did the ball peen hammer get its name and Where does the term ball peen come from?

This is recorded merely for the benefit of those who don’t know one kind of hammer from another.

But this one is used chiefly by metalworkers.

It is one in which the side opposite the face or flat surface of the hammer or sledge is rounded or ball-shaped.

Peen, that is, also sometimes spelled pane, pean, or pein, designates that end of the head of a hammer, and it may be pointed, sharp, thin, or ball-shaped.