Beat the tar out of you

Where did the phrase "To beat the tar out of you" come from?

Previous discussion: One person said tar = stuffing. So it is another way of saying beat the stuffing/insides out of someone. Another thought since tar (What the tar!) = eternal damnation. Beating the evil out and the good in. www.phrases.org.uk bulletin_board 9 messages 814.html I think "beating the tar out of someone" is a "cleaned up" version of "beating the sh*t out of someone."