You need to provide the name of a branch (or other commit identifier), not the name of a remote to git rebase.
E.g.:
git rebase origin/master
not:
git rebase origin
Note, although origin should resolve to the the ref origin/HEAD when used as an argument where a commit reference is required, it seems that not every repository gains such a reference so it may not (and in your case doesn’t) work. It pays to be explicit.