Hem and haw

Isn't the Internet wonderful? I just used that phrase, meaning to hesitate, in an e-mail and it struck me that I had no idea what it came from. So I looked it up and the original British version is "hum and haw." In the American, "hem' is short for the throat clearing "ahem," and "haw" refers to a overly proper and hesitant way of speaking (haughty?)