Synonyms for valiant include "heroic" and "courageous," so it isn’t surprising that those who serve in the military often are called valiant. The 14th-century French origins of the word are "bold" or "of worth," which makes the adjective valiant a good one for describing ordinary people who put all they have into something, making their efforts valiant, even if they fail. The Plymouth Valiant, by the way, was considered a strong and successful car, though valiant usually refers to people.