I looked it up sometime ago and it turns out both usages are actually legitimate, and they both date from around the same time. I never say "from whence", though, because I don't like how it sounds.
Maiden, I shall take arms and defend thee from these cravens. (Usage dating before US Constitution. The phrase, "TO ARMS!" is noted, as well with King Richard III, and was also used in reference to the "Coat of Arms," a family crest adorned typically in weapons.); <Reads the US constitution>; "I say, good man, from whence is the term "arms" defined as firearms within the constitution?"
