I was thinking yesterday that there might be more to the common saying “asking for her hand in marriage.” Doing a few searches and I found that some believe it comes from a medieval ritual known as handfasting. Today it has been adopted by certain Neopagan groups as part of their engagement or marriage rituals, but it has a history which dates back to the Middle Ages in the Christian context, and is certainly much more ancient still1. Apparently this practice has fallen out of usage and been lost among most of mainstream Christianity, except in Eastern Orthodoxy.
The modern handfasting ritual typically consists of tying the right hands of the couple to be betrothed or wed with a ribbon or cord while the couples exchange their vows. This is also probably the origin of the common phrase, “tying the knot.” In some cases, all four hands are tied together to make a figure 8 when viewed from above, the symbol of infinity or eternity (as in the photo on the right)2.

There is a good treatment on the history of Medieval handfasting on MedievalScotland.org, in which the author quotes from A.E. Anton:

Among the people who came to inhabit Northumbria and the Lothians, as well as among other Germanic peoples, the nuptials were completed in two distinct phases. There was first the betrothal ceremony and later the giving-away of the wife to the husband. The betrothal ceremony was called the beweddung in Anglo-Saxon because in it the future husband gave weds or sureties to the woman’s relatives, initially for payment to them of a suitable price for his bride but later for payment to her of suitable dower and morning-gift. The parties plighted their troth and the contract was sealed, like any other contract, by a hand-shake. This joining of hands was called a handfæstung in Anglo-Saxon, and the same word is found in different forms in the German, Swedish and Danish languages. In each it means a pledge by the giving of the hand. ….
…After the consents had been exchanged ‘the curate with the consent of both parties with their hands joined betrothed the said David and Janet who took oath as is the custom of the Church‘. In fact, the ceremony of joining hands became so closely associated with betrothals in medieval times that in Scotland, and apparently the north of England, the ordinary term for a betrothal was a handfasting. The use of the term in this sense persisted in Elgin as late as 1635.3