Judah was a slave in Ancient Rome that helped Jules and Verne Brown get their father out of prison. When Marty gives him the chariot as he gets back in the DeLorean, and asks for his name, he reveals it to be Judah Ben-Hur, causing Marty to discover who he is.
Behind the scenes
Judah Ben-Hur, however, is as fictional as Marty. In 1880, American author Lew Wallace published the historical novel Ben-Hur: A Tale of the Christ. The book was a bestseller and was later adapted into several films, including the popular 1959 movie, Ben Hur.