enlig - the s is a so-called foge-s, used to connect words in a compound. It's the same en as in "one", originally, so the meaning was basically similar as in one and the same. German has ähnlich for "similar" in essentially the same way.
And you're right: it does feature as an occasional suffix. But not really on its own as with your rabbbit example - we tend to use it mostly for established words, or in the "accordingly" sense when used in new words.
Edit: Of, and of course, English has "only" from the same etymology. :)