Scrapie
The name scrapie is derived from one of the clinical signs of the condition, wherein affected animals will compulsively scrape off their fleeces against rocks, trees, or fences. The disease apparently causes an itching sensation in the animals. Other clinical signs include excessive lip smacking, altered gaits, and convulsive collapse.
Thomas Crapper
The word "crap" is actually of Middle English origin and predates its application to bodily waste. Its most likely etymological origin is a combination of two older words, the Dutch "krappen": to pluck off, cut off, or separate; and the Old French "crappe": siftings, waste or rejected matter (from the medieval Latin "crappa," chaff). In English, it was used to refer to chaff, and also to weeds or other rubbish. Its first application to bodily waste, according to the "Oxford English Dictionary", appeared in 1846 under a reference to a "crapping ken," or a privy, where "ken" means a house.