子弹
zǐ dàn · HSK 5
bullet
🔫 子 = small/child + 弹 = projectile; small projectile = bullet
子 here means small thing (as in 椅子 chair-thing), and 弹 means projectile or to shoot. Combined, a small shootable thing is a bullet. Same 弹 appears in 炸弹 (zhà dàn, bomb).
子 — pictograph of a baby/child with arms out
子 began as a pictograph of a swaddled infant with a large head and outstretched arms, originally meaning 'baby' or 'child.' From there it broadened to 'son,' 'offspring,' and a respectful suffix for masters like 孔子 (Confucius). It also became one of the twelve earthly branches.
弹 — bow 弓 + single 单 (phonetic)
Originally a pictograph of a bow with a pellet ready to launch, 弹 depicted a slingshot or pellet bow. The form was later regularized as a phono-semantic compound: 弓 (bow) gives the meaning of shooting or springing, while 单 supplies the sound. Modern senses—bullet, to pluck, to spring—all extend from this shooting/elastic-release idea.