During the Tang Dynasty, the imperial examination was the primary path for scholars to become officials. After ten years of hard study in obscurity, achieving fame and success in a single day was the greatest dream of every scholar.
In the year 875, during the reign of Emperor Xizong of the Tang Dynasty, a routine imperial examination was held in the capital Chang'an, presided over by the prominent minister Cui Hang.
Candidates who had passed the preliminary exams flocked to the capital for the imperial examinations. Among them was a talented scholar named Cui Xie, who felt confident after completing the three rounds of tests and eagerly awaited the results.
When reviewing Cui Xie's exam paper, Cui Hang found his writing mature and his talent overflowing, praising him highly and thus admitting him. On the day the results were posted, Cui Xie saw his name on the list and was overjoyed.
According to the custom of the time, all successful candidates became disciples of the chief examiner, who was their "esteemed teacher."
After Cui Xie passed the imperial examinations, he followed custom by visiting his benefactor to express gratitude for his guidance. When Cui Hang saw Cui Xie, he was overjoyed.
As luck would have it, the two characters "Hang" and "Xie" together form a word that originally meant nighttime mist or dew. Now, the two men's names happen to combine into "Hangxie," which is truly a rare coincidence.
At that time, people buzzed with gossip, saying Cui Hang and Cui Xie were "Hang and Xie in one breath," likening the teacher and student to nighttime mist and dew clinging together. It was because they shared the same temperament that Cui Hang admitted Cui Xie.
"The idiom 'Sharing the Same Vapor' originally described like-minded people banding together
Source: *Tang Yulin*, "Supplement"
Meaning of the Idiom: Later, the Chinese idiom "沆瀣一气" came to describe how like-minded people band together.