hardened dirt or clay, cluster
埵 centers on earth that has been packed or hardened into a solid mass, like a clod of clay or a cluster of soil. The cluster sense extends naturally from the idea of earth particles sticking together.
埵 combines 土 (earth) with 垂, which likely contributes the sound and may suggest the idea of something hanging or drooping, possibly referring to clumps of earth that hang together. The exact historical development is uncertain.
The left side is earth 土, and the right side 垂 looks like something heavy hanging down. Picture a clump of hardened dirt hanging off a shovel: it's a cluster of packed clay.
For タ, imagine a hardened clod of dirt shaped like the letter T: T -> タ, and the T-shaped clay cluster sits on the ground.
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