According to Wikipedia (which, of course, knows everything) Edward Aloysius Murphy, Jr. (January 11, 1918 – July 17, 1990[1]) was an American aerospace engineer who worked on safety-critical systems. He is best known as the namesake of Murphy's law, which is said to state, "Anything that can go wrong will go wrong."
But with that name, I guess we'd say Irish-American.