書留
かきとめ · kakitome · JLPT N2 · noun
registered mail
✉️ 書 = write, 留 = keep or hold: a letter you write and keep on record
留 means stay or keep, as in 留学 (studying abroad, staying overseas). Registered mail is kept on record and must be signed for.
留 — 卯 (top) + 田 (field)
Originally a phono-semantic compound: 田 (field) suggests staying on the land, with 卯 hinting at the sound. Over time it came to mean 'remain, stay, keep,' as in keeping someone on the land or holding something in place. Modern uses include 留学 (study abroad) and 保留 (retain).