叶子
yèzi · HSK 4
leaf
🍃 叶 = leaf + 子 = noun suffix; literally 'leaf-thing'
叶 carries the meaning 'leaf' on its own; 子 is a common noun-forming suffix (as in 桌子 table, 椅子 chair). So 叶子 is just the everyday word for a leaf, the countable object.
子 — pictograph of a baby/child with arms out
子 began as a pictograph of a swaddled infant with a large head and outstretched arms, originally meaning 'baby' or 'child.' From there it broadened to 'son,' 'offspring,' and a respectful suffix for masters like 孔子 (Confucius). It also became one of the twelve earthly branches.