please look at this!
today I found a very interesting phrase when I reading book which was "tie the knot", I look up the dictionary then I know the meaning is getting marrage. The very interesting thing is in chinese there also is a word named 喜结连理 which means the branches of trees growing together that indicate the marriage. Very funny! My question is in your opion why the frase "tie the knot" means marrage and how to think about it, of if there is some special meaning in it?

Question

please look at this!
today I found a very interesting phrase when I reading book which was "tie the knot", I look up the dictionary then I know the meaning is getting marrage. The very interesting thing is in chinese there also is a word named 喜结连理 which means the branches of trees growing together that indicate the marriage. Very funny!  My question is in your opion why the frase "tie the knot" means marrage and how to think about it, of if there is some special meaning in it?

Answer

There is another saying "ball and chain".  It means the person I am permanently tied to and holds me back.  This is because prisoners (especially in the past- not today) were tied to a metal ball that kept them from running quickly.  She or he is my prison.
In that way- but less silly- you are becoming attached - tied.  Two large groups (families) become attached through the thin line (of two people tied.)