当初
dāng chū · HSK 3
originally
⏰ 当 = at/when + 初 = beginning/first; 'at the beginning'
当 marks a point in time (at/when), and 初 means first or initial (the radical 衤cloth + 刀 knife = the first cut of cloth when making a garment). Together: at the original moment, back then.
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.
初 — clothes radical 衤 + knife 刀
初 combines 衤 (clothes) and 刀 (knife), depicting the act of cutting cloth to begin making a garment. From this concrete image of starting a tailoring task came the extended meaning 'beginning' or 'first'. It is an associative compound, not phonetic.