ground, fertile land
堉 centers on earth that is rich and productive: ground that is fertile and good for growing things.
堉 combines 土 (earth, soil) with 育, which likely contributes the sound and the idea of nurturing or raising, suggesting earth that nurtures growth.
The left side is earth 土, and the right side is 育 (nurture, raise). Picture rich soil nurturing seeds into healthy plants: 堉 is fertile ground.
For イク, imagine fertile ground that makes plants grow quickly, like an 育 (いく) nurturing them: 育 -> イク, and the earth itself is fertile.
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