洪乔捎书 — “To fail to deliver what was entrusted, especially messages”

During the Jin Dynasty, there was a prefect named Yin Xian, whose courtesy name was Hong Qiao, serving in Yuzhang. When he was leaving his official post, many people, knowing he was returning to his hometown, entrusted him with letters to be delivered to their families and friends.

At that time, there were no postal services, so people relied on acquaintances to carry messages. Hong Qiao politely accepted over a hundred letters. However, upon reaching Shitou Isle, he secretly threw all the letters into the river.

Later, when recipients did not receive their expected correspondence, people began to associate the failure to deliver letters with Hong Qiao's name, and thus the idiom 'Hong Qiao delivering letters' came to signify someone who is entrusted with a task but fails to carry it out, acting untrustworthy.