切る
きる · kiru · JLPT N5 · verb-godan
to cut
✂️ kiru: the kiri in harakiri (belly-cutting) is this same verb
Harakiri = hara (belly) + kiri (cutting), the noun form of kiru. The kanji 切 holds 刀 (blade) on its right side. Hanging up a phone uses the same verb: you cut the line.
切 — 七 (phonetic) + 刀 (knife radical)
切 is a semantic-phonetic compound: 刀 'knife' gives the meaning of cutting, while 七 supplies the sound. The original sense was to slice or cut with a blade. From there it extended figuratively to 'close to' (as in pressed against) and 'urgent/earnest', as in 切实.