The Germans in the American Civil War: With a Biographical Directory by Wilhelm Kaufmann has a reference to Gustavus Lightfoot of the 12th Missouri. Kaufmann lists him as Gustavus Leichtfuss, indicating that possibly Lightfoot was the anglicized spelling of his name. I had wondered about this before I saw the reference in this book; Lightfoot certainly didn't seem like a likely name for an officer in a regiment that was almost entirely, if not entirely, ethnic German.
I don't own this book, so I can't check this for sure right now. I've flipped through it at the library a couple of times, but just haven't had the time to get into it more deeply.
Anyway, this might be a reference worth checking out.