Following up on a suggestion to bring back classic (or at least old) posts, here's one I'd completely forgotten: "Was Strunk imitating Quintilian?", 3/28/2009. Bill Walderman asked whether the "rule" prohibiting clause-initial position for however might have been an imitation of Latin and Greek second-position elements, and especially the treatment of autem.
After a two-cup-of-coffee research project, I concluded that Bill's idea is a plausible one:
[T]his whole line of reasoning is speculative at best. But it might help explain where Will Strunk got the strange impulse to declare that Mark Twain used however incorrectly two-thirds of the time.