一度
いちど · ichido · JLPT N4 · noun
once
☝️ 一度 = one (一 ichi) + degree/occurrence (度 do): one time
度 counts occurrences, so 一度 is literally one occurrence. Swap the number to count further: 二度 (nido) is twice, 三度 (sando) is three times. The same 度 also means degrees, as in temperature.
一 — single horizontal stroke
一 is one of the simplest pictographs in Chinese, depicting a single horizontal line to represent the number one. It has retained essentially the same form since oracle bone script over 3,000 years ago. By extension it also means 'first,' 'whole,' or 'same.'
度 — 广 (shelter) + 庶 abbreviated (phonetic)
Originally depicted a hand measuring length under a shelter, meaning 'to measure' or 'a measure/standard.' From this came extended senses like 'degree,' 'extent,' and 'to pass through' (as in passing time). The reading 'dù' means degree/measure, while 'duó' preserves the older verbal sense of measuring.