The literal sense of zhong is to give one's whole heart: to do one's utmost when acting for another. At first it spoke mainly of a minister's duty to his lord.
Around 500 BCE Confucius said "ministers serve their lord with loyalty" and took loyalty and reciprocity as the single thread of his teaching, and zhong became a part of Confucian political ethics.
Around 1176 Lu You of the Southern Song wrote "humble in rank, I dare not forget my worry for the country". His post was not high, yet what he kept in mind was the country. Here loyalty is carried from the ruler to the country.
Loyalty is the class in the chapter on Values on zhong, loyalty widening from a duty to the ruler into a duty to the country. Confucius said "ministers serve their lord with loyalty" and made loyalty and reciprocity the thread running through his teaching; in the Southern Song Lu You wrote "humble in rank, I dare not forget my worry for the country", extending loyalty from the ruler to the nation.
