Getting back to Dave's original question, I think farter should be allowed.
The Shorter Oxford lists it as a derived word, without any further explanation, but I'm intrigued to see that the Australian and New Zealand editions of the Oxford both list this word as a down-under colloquialism for a bed or sleeping bag. This is something I've never heard of, and I suppose you hadn't heard of it, Dave, or you would have mentioned it in your original, very informative post. Furthermore, I can't find a reference to this usage in any other guides to Australian English. What say you, antipodean forumites? Has anyone ever heard of farter being used for a bed or sleeping bag?