Catspaw:

Ever use a word thinking it's commonplace, only to learn from listeners' blank looks that it's obscure? Just happened to me in class Friday with "catspaw." It surprised me, though quick Nexis and Google searches confirm that it is indeed pretty uncommon; I found only about 15 references, setting aside proper names, in all Nexis-accessible 2006 newspaper articles. Google reports 200,000 references, about the same as for "dogsbody" (which I knew was obscure), but many of those seem to be to proper names, cat's paws, and cat's paw mussels. Don't know why I thought the word was relatively normal.