I accidentally created a local branch named origin/foo. Now what?

I have a remote branch named foo, that is not tracked in the current client.

I did git checkout -b origin/foo, and this created a local branch named origin/foo. This looks bad, since up until now all my local branches didn't have a origin/ prefix.

I tried to delete this local branch by running git branch -d origin/foo, but it complained that the branch is not fully merged. I'm afraid that if I'll force it using -D, it will actually delete the remote branch.

How do I clean up this mess?