Late Middle Chinese origin
Source-reported/itʉ/ → /it͡sʉ/ → /it͡su/ From Middle Chinese 一 (ʔiɪt̚).
Sources for this account (2)
- Wiktionary: 一CC-BY-SA-4.0 · retrieved 2026-10-15
- JMnedict entry 5123265CC-BY-SA-4.0 · rev. 2026-10-15 · retrieved 2026-10-15
