Handfasting: The term "tying the knot" originates with the practice of handfasting. During the ceremony, the couple's hands are tied together with one or several colored cords or ribbons, symbolizing the desire of the couple to be united. The cord is often kept by the couple in a box or ornate bag as a reminder of their vows.
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M's Star Wars Wedding by Jedilynn82, via Flickr and they have a handfasting ceremony! I want to do that!