There is a lot of variation within species. Most American water-horehounds are much less fuzzy than this one. If it were not for the forward pointing teeth on the leaves, it could be a European water-horehound, which is pretty hairy. The European species has been introduced here, and the two do produce hybrids. Could this be one of those? With the right equipment, including a super computer, we might figure it out. Otherwise, not every plant puzzle has a final answer.