variable unit of land measure
垧 centers on a variable unit of land measurement, used historically to describe an area of fields or farmland.
垧 combines 土 (earth, soil) with 向, which likely contributes a phonetic element. The character is used for a land measurement, fitting the earth radical.
The left side 土 is earth or soil, and the right side 向 suggests direction or facing. Picture measuring a plot of land by facing each side and pacing it out: 垧 is a unit of land measure.
For ケイ, imagine a surveyor using a cane to measure the land: cane -> ケイ, and the cane helps mark the variable unit of land.
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