Meaning of drilling

Why is a German gun with both rifle and shotgun barrells called a drilling? First thought was reference to military exercise (drill). Second thought was reference to it shooting as straight as if using a drill to make a hole. Third thought was that it's a German word, either unique to this definition or an old word that was given new meaning. Anyone know?

Thanks for all the responses. I assumed the configuration was for flexibility. If you're out deer hunting and see a game bird you have an appropriate firearm and vice versa.

There was a program a few years ago where european youth interested in farming could work for a summer on an american farm. One of the participants asked how a young person here could get started farming. I explained how we often farm on shares or contract for deed. He said those options weren't available in germany, because big corporations owned all fhe farm ground. So the more things change, the more they stay the same. Instead of land barons they now have corporate farming. I wonder if the corporations allow hunting? While it would be additonal revenue, liability risk might be too high.