Many may have assumed that the saying "tie the knot" means to become bound together by marriage — similar to how two strings can be knotted together. But this is only partially true. There's a much richer cultural practice behind this common phrase.

According to Brides, "tying the knot" refers to a Celtic wedding practice that dates back to 7000 B.C. and is called handfasting. The Culture Trip notes that handfasting may have historically only symbolized a couple's intent to marry, similar to an engagement today, to test their marriage compatibility before officially conjoining. These days though, handfasting usually takes place on the day of the wedding or in vow renewal ceremonies.

A video demonstration by Jane Bechtel, a wedding celebrant from Humanist Society Scotland, shows that there are a variety of ways to perform Celtic handfasting. However, they all involve making knots with fabric or cords to represent unity.