单独
dāndú · HSK 4
individually
🚶 单 = single + 独 = alone; together: solo/by oneself
单 carries the sense of single/one, and 独 means alone or solitary. Stacking the two doubles down on the idea of being on one's own — acting individually, without company.
单 — 叩 (two mouths 口) over 甲 (shield/armor)
Originally a pictograph of a forked hunting weapon or shield with two prongs at the top. The ancient form shows a Y-shaped tool, later stylized into the modern shape. The meaning shifted from the weapon to 'single' or 'one,' possibly because it was a single-handed tool.
独 — dog radical 犭 + 蜀 (phonetic)
A semantic-phonetic compound: 犭 (dog) gives the meaning, since dogs were thought to fight when kept together and so were often kept singly, while 蜀 supplies the sound. The original sense was 'solitary dog,' which broadened to 'alone, single, only.'