Actually, the word is older than both writers. The Oxford English Dictionary traces muggles back to the 13th century, when muggles meant "tails." By the 20th century, the word had come to mean marijuana. In the 1920s a pot smoker was called a mugglehead. In the 1930s Louis Armstrong had a song called "Muggles." And in 1960 a children's book called "The Gammage Cup," featuring a character named Muggles, was a Newbery Award honor book.