補足
ほそく · hosoku · JLPT N1 · noun
addendum
📎 補 (fill up) + 足 (foot/enough) = add what's missing to make it sufficient, like a footnote that fills the gap
補 means to patch or fill a gap; 足 means foot or sufficient. Together: adding what a thing lacks so it becomes complete. Sounds like 'hoso-ku', close to 'hose' (a hose that tops up the tank).
足 — top 口 (mouth/enclosure) + bottom 止 (foot)
Originally a pictograph of a leg and foot, with the upper square representing the knee or shin and the lower part 止 depicting the foot itself. It primarily means 'foot' and by extension 'sufficient' or 'enough,' a meaning shift likely from the idea of standing firmly or having a solid footing.