mediocre, busy, occupied, roller
磟 centers on a stone roller used for leveling or crushing, which connects to the idea of being busy or occupied with repetitive work. The 'mediocre' sense likely comes from the monotonous, unremarkable nature of such labor.
磟 combines 石 (stone) with 翏, which likely contributes the sound. The exact historical development is uncertain, but the stone radical suggests a stone implement, consistent with the 'roller' meaning.
A stone (石) roller (翏 suggests a heavy, repetitive shape) that flattens everything to the same level—mediocre and busy work.
For リク, imagine a stone roller making a rhythmic 'rick-rick' sound as it rolls: rick -> リク.
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