～区
～く · ～ku · JLPT N4 · noun
district
🏙️ 区 = a boxed-off area: Shibuya-ku, Shinjuku-ku — ku marks a city ward
区 (ku) means a divided section; its old form 區 was an enclosure holding 品, goods sorted into compartments. As a suffix it names a city ward: 渋谷区 Shibuya-ku, 新宿区 Shinjuku-ku. Same root as 区別 (kubetsu), to tell apart.
区 — enclosure 匚 + 品 (items)
Originally a pictograph of items (品) hidden inside a container (匚), meaning to store or conceal. The sense extended to a bounded space, then to an administrative district or area. As a surname read Ōu, it preserves the older 'hidden/enclosed' nuance.