必修
ひっしゅう · hisshuu · JLPT N1 · noun
required (subject)
必 — heart 心 + slash 丿
Originally depicted a handle or marker driven through something, suggesting a fixed standard. The form was later reanalyzed as 心 (heart) with a stroke through it, reinforcing the sense of inner certainty. It came to mean 'must' or 'certainly'.
修 — 亻 person + 攸 (phonetic) + 彡 hair/decoration
修 combines 攸 (a phonetic component originally showing a person being washed) with 彡, which depicts flowing hair or ornamental strokes. The 彡 element suggests grooming, polishing, or adorning, giving 修 its core meaning of cultivating, repairing, or refining oneself or things.