An American English Pondering

[gnomi]

I see "drug" periodically for "dragged," as in "It was all fine and dandy until we were drug away," and I recognize it as regionalism. But here's where I get to wondering: where did it come from? Are there -ag/-ug pairs in AmE for the present/past? I can think of a bunch of -ang/-ung sets (ring/rang/rung; sing/sang/sung; hang/hung; spring/sprang/sprung and so on), but I can't come up with any -ag/-ug sets.

Anyone? Bueler? ;-)