相当
そうとう · soutou · JLPT N3 · noun
considerably
⚖️ 相 mutual + 当 match: two things that match up, so worth ~, then considerably
相当 first meant equal to or worth (この金額に相当する, worth this amount). Something that measures up to a high standard is a lot, so it came to mean considerably or fairly: 相当難しい, pretty hard. Sounds like so-toe: so very much.
当 — small ⺌ + crown 冖 + hand 彐 (simplified from 當: 尚 + 田)
Originally written 當, combining 田 'field' with 尚 as a phonetic. The early sense was 'to match' or 'face' a field of equal value, extended to 'correspond to', 'ought to', and 'serve as'. The simplified form 当 streamlines the upper 尚 component.