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.
Tracker scrape
A scrape, or tracker scrape, is a request sent by a BitTorrent client to a tracker. A request is sent, connection to the tracker is established, information is exchanged, then the connection is closed. The request does something like a "wipe" or a "pass" over the tracker, and then the tracker sends information back to the client.