Li Dai Tao Jiang (The Plum Tree Suffers for the Peach Tree)
There was a folk song, the last two stanzas of which ran as follows:
One family has five brothers, all in the position of Attendant to a Minister.
Every five days they gather together for a reunion, which attracts crowds of onlookers along the road;
Look, even the bits and straps of their horses are adorned with gold to vie with each other for splendor!
Now, a peach tree grows by a well, and next to it a plum tree.
When the worms come to gnaw at the root of the peach tree, the plum tree suffers them to gnaw at its own and eventually dies ossified.
If trees know how to sacrifice for others, it is a real surprise that brothers should cast aside brotherly feelings.
This idiomatic expression, however, is generally used to mean “substituting for another” only. It has lost its original sense altogether.