理 (lǐ): The original meaning of this character relates to the patterns or grain found in a piece of jade. This evolved to mean “reason,” “logic,” “truth,” and most importantly, the “principle” or underlying natural order of things. Imagine the grain in a piece of wood or the veins in a leaf—that's a physical manifestation of its 理 (lǐ).
学 (xué): This is a fundamental character meaning “to study,” “learning,” or “a school of thought.” It depicts a child under a roof, learning.
When combined, 理学 (lǐxué) literally means “the study of Principle” or “the School of Principle.” This name perfectly captures the philosophy's central focus: understanding the rational, organizing principle that governs the cosmos, society, and the individual self.