Abstract
The idiomatic expression "Dankin-no-chigiri (断金の契り)" means a firm friendship. As an early instance, we are able to find this expression in "Shui Jin Zhu (水經注)" which is a Chinese document written in the early 6th century. In Japan, some documents written in the first half of the Heian era confirmed that Buddhist priests had used this expression. Sometime during the Heian era, this expression came to mean not only the firm friendship but also the close relationship between brothers. In the end of the 12th century, a story narrating the reason why this expression came to mean the close relationship between brothers was created. The story was narrated by Buddhist priests when they were preaching Buddhism to common people. A brief outline of the story is as follows:
One day, two brothers visited their father. The father gave many nuggets of gold to each of them. On their way home from their father’s house, the younger brother threw away his gold. The elder brother asked him "why did you do so?" The younger brother broke into tears and said "An evil thought flashed through my mind. I was going to kill you and rob you of your gold. I realized that a desire for wealth made me to contrive this horrible evil design. That was why I threw away the gold." Then the elder brother said "I had the same thought as you had", and threw away his gold.
After that, the close relationship between brothers came to be expressed by "Dankin-no-chigiri".
Dan (断) means to cut or to stop, and Kin (金) means gold or metal. In the expression "Dankin-no-chigiri" there is a play on words, with Dankin meaning both "hardness that can cut off metal" and "strong willpower that can stop desire for wealth".
In this paper, I have made it clear that the story was created by Buddhist priests, and handed down by preachers.
