1. excrement, dung
2. something regarded as being morally offensive
Etymology: from old French ord, filthy, which came from Latin horridus, frightful. Think 'horrid'.
For some reason, I keep thinking 'ordure' is related to 'odor'. It isn't. But when I think of the word, I think of "the odor of excrement"...which at any rate gets me to the right visceral reaction to go with the word's actual meaning.