忠

A phono-semantic compound with:

心 (“heart, mind”) as the semantic element;

中 (“center, middle”) as the phonetic element.

There is also an interpretive explanation as an associative compound: a “heart (心) that is centered and not biased (中),” symbolizing fairness and integrity.

Originally meant “true heart” or “sincere feelings,” but over time came to primarily mean “loyalty to the ruler or the nation.”