palm
桹 centers on a type of palm tree, specifically the tall, straight-trunked palm used for timber or its wood.
桹 combines 木 (tree/wood) with 良, which likely contributes the sound. The character specifically denotes a type of palm tree.
The tree radical 木 beside 良 suggests a good, useful tree: a tall palm providing straight timber.
For ロウ, imagine a row of palm trees lining a road: row -> ロウ, and each tree is a tall 桹.
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