It must do strange things to someone for their name to detach from their person and take on a meaning of its own. George Orwell didn’t live long enough to see his name become an adjective; Tony Blair and Margaret Thatcher did, and look what happened. Worse than becoming an adjective, though, must surely be becoming a noun, and for that noun to eclipse them entirely. It’s possible, now, to use the word “quisling” without ever suspecting it wasn’t always a generic term for a traitor and collaborator. But it referred to a Norwegian politician, Vidkun Quisling, whose choices during...