This webpage -
http://static.namesdatabase.com/names2/O/E/Oeller.htmlgives some misspellings (and variants?) of the German surname Oeller, which, I imagine, has something to do with oil; a vendor of olive oil perhaps, or an extractor of vegetable oil.
There is also a dialect word, Oellre, which appears to be cognate with the standard German elter (elder?). Perhaps someone with a good knowledge of the language could help you with this.