2. What you do in order to catch the snitch.
In Quidditch (of the Harry Potter fame), the "bludgers" are two 10-inch iron balls which are enchanted to attack the living thing closest to it. The job of the beaters is to take a magically-reinforced bat and whack the bludgers as far away from their team as possible (so it would recognize an opponent as being closest and go after them). Over time, the blatant implied innuendo became commonplace slang, and the Quidditch act of whacking two oversized balls with a "magically-reinforced bat" named "beating the bludgers" was applied elsewhere.