椰子 (yēzi) = coconut, 树 (shù) = tree. Just stack them. The radical 木 in 椰 even shows you it is a tree-word.
culture
Hainan island (海南) is China's coconut country — its provincial flower is the coconut tree blossom and the local capital 海口 is famous for fresh 椰汁 (coconut juice).
