In 496 BCE, Confucius was appointed Grand Minister of Crime (the highest judge) and acting prime minister of the state of Lu. He devoted himself wholeheartedly to his duties, greatly transforming the customs and morals of Lu.
The achievements of Confucius so alarmed Duke Jing of Qi that he specially selected eighty beautiful singing girls and sent them as a gift to Duke Ding of Lu, intending to corrupt the ruler's will. The scheme worked exactly as planned—Duke Ding of Lu became completely immersed in music and pleasure, spending his days indulging in entertainment and even neglecting to attend court.
Confucius, deeply disappointed by the situation, followed his disciple Zilu's advice and traveled to the State of Wei. Duke Ling of Wei, who had long heard of Confucius's great reputation, welcomed him warmly and offered him the same generous salary he had received in the State of Lu.
Confucius' disciples were delighted to see their teacher had found a place to stay, and asked him what he would do first if he became the chief minister of Wei. Confucius replied, "I believe the first priority is to rectify names and ensure that words match reality. That is, proper titles must be used and speech must be reasonable, so that the people will have trust."
Unexpectedly, Duke Ling of Wei's warm welcome to Confucius was merely a passing gesture, and he never actually appointed Confucius to a significant role. Finding himself once again without a proper position in Wei, Confucius could not help but feel deeply disheartened.
Soon, someone spoke ill of Confucius before Duke Ling of Wei, forcing Confucius to leave the state as he could no longer stay there.
Later, people used the idiom "Just and Proper" to indicate that what one does has legitimate and sufficient reasons.
Source: *The Analects*, Chapter "Zilu"
Meaning of the Idiom: Later, the Chinese idiom "名正言顺" came to describe what one does has legitimate and sufficient reasons.