Okay, so there I was doing a search on the phrase, The Buck Stops Here because I was thinking about that other phrase, “It’s not my fault.” But more on that later… Once you search on the buck stops here you end up at a Harry S. Truman page, naturally. On this page from the Truman Presidential Museum and Library, you’ll find this quote from Harry: “The President–whoever he is–has to decide. He can’t pass the buck to anybody. No one else can do the deciding for him. That’s his job.”
So, he didn’t use the word with the “er” ending, but clearly he was a decider.