約束
やくそく · yakusoku · JLPT N4 · noun
agreement
🤝📅 約束 = bind (約) + bundle (束): a promise ties you up tight
約 means to contract or agree, and 束 means a bundle tied with cord. Both characters carry the sense of binding, so a promise or appointment is something you are doubly tied to. Sound hook: yaku-soku, like a yak who so-keeps his word.
束 — 木 (tree) with 口 wrapped around middle
Pictograph of a bundle: a tree or sticks (木) tied together with a band or rope (depicted by the enclosing 口 in the middle). The original sense was 'to bind' or 'a bundle,' which extended to meanings like 'to restrain,' 'to control,' and the measure word for bundled things.