I had always been of the assumption that handfasting was a primarily Celtic tradition that was adopted into the Christian liturgy as the church spread into the Celtic lands of Gaul, Britain, Ireland and Scotland. If you look at old liturgical manuals of the Catholic Church you will find the practice to have been adopted into the ceremonies although it is the stole of the priest which is used and not a swatch of tartan.

I also think we should consider this in terms of sets and subsets. Things Scottish are a subset of things Celtic. All things Scottish should be considered a part of the larger spectrum of things Celtic. But not all things Celtic are Scottish. However, in this instance the practice is both found within the larger set of things Celtic and within the subset of things Scottish. Just because it is also found within other Celtic Subsets and was even adopted by non-Celtic groups after exposure to the practice, does not make it any less Scottish. It just means that it's also a part of the practices of the other groups.

I feel that one can just as truthfully state that the practice is Scottish as one can state that it is Irish or Celtic or Pagan or even Christian since the pagan practice was adopted by the church into the liturgies.

Also, just because a similar cultural expression is found in two different cultures does not mean that one necessarily borrowed from another. Just as species can sometimes independently evolve similar adaptations to fill similar evolutionary niches (despite being completely unrelated) so too could a practice such as handfasting evolve independently. It is a rather self-evident idea. What does one do when one wishes to join to pieces of wood? One ties them together. And since our cultural ceremonies are often borrowed or based on common aspects of life for the roots of their symbolism, what might someone do to symbolize the joining of 2 people or 2 families? Why, tie them together of course!

As an aside, I've seen the bride and grooms hands bound together using rope in a Korean buddhist ceremony and was told that the practice originated as an ancient part of THEIR tradition. Considering the distance and the mutual claims of antiquity, I am inclined to believe that both developed the practice independently.

Okay, all this is to say why can't the practice of handfasting be an ancient Scottish tradition as well as an ancient Korean tradition and an ancient continental Pagan tradition? Is it so unbelievable that they might have had some independent development of culture that lead them to similar symbols? And why must only one group get credit?