Someone has fed Google some trash directed at your site.
Who did the feeding I don't know.
But once Google has a url it goes out and asks the server hey server do you have anything for me at url.
If the server answers 200 and here it is, Google is happy and stashes what it got under the url as content to be indexed.
It appears that servers answer 200 when they shouldn't or that they don't come with clear setup instructions or that they have poor default setups.
Up until Google stopped ignoring query strings it made little difference, now you get duplicate content as a result.
With the trailing slash the duplicate content issue again comes into play.
The same problem can occur in other situations as well.
You might wish to visit the Apache forum and go through the postings there.