心得る
こころえる · kokoroeru · JLPT N2 · verb-ichidan
to understand
心 (heart/mind) + 得る (obtain) = to obtain it in the heart, so to understand thoroughly
Kokoroeru combines kokoro, meaning heart or mind, with eru, meaning to obtain or get. Something taken into your heart is fully grasped, so it means to understand deeply.
心 — pictograph of a heart with chambers and aorta
心 is a pictograph showing a stylized heart, with strokes representing the organ's chambers and the aorta at the top. Originally meaning the physical heart, it broadened to cover mind, feelings, and intentions, since ancient Chinese thought located thinking and emotion in the heart.
得 — 彳 (step) + 旦 (sun/day) + 寸 (hand)
Originally depicted a hand 寸 reaching for a cowrie shell 貝 (later simplified to 旦), with 彳 'step' added to show going out and obtaining something. The core meaning is 'to get' or 'obtain'. The reading děi extends this to 'must/have to' — what one is obliged to get done.