四角
しかく · shikaku · JLPT N3 · na-adj
square
🔲 四角 = four (四) + corner (角): a four-cornered shape
四 (shi) means four and 角 (kaku) means corner or angle, so the word literally says four corners. The same 角 appears in 三角 (sankaku), three corners, which is a triangle.
四 — enclosure 囗 + divide 八
Originally 四 was written as four horizontal strokes (亖), a simple tally for the number four. The current form, showing 八 (divide) inside an enclosure 囗, was borrowed during the Zhou dynasty and gradually replaced the older tally form. The shape is unrelated to its meaning today.
角 — pictograph of a horn
角 is a pictograph of an animal's horn, with early oracle-bone forms clearly showing the curved, ridged shape of a horn. From 'horn' it extended to mean corner, angle, and by metaphor a role or part (as in a stage role). The reading jiǎo covers most of these senses.