Start with an ordinary hat whose brim lies flat all round. Now fold that brim upwards and pin it, two folds or three, and the outline stops being a circle: it becomes a shape with corners, a triangle sitting on someone's head. That folded, cornered shape is what the name holds on to. It explains why the hat belongs to old portraits of officers and sailors, and why the same three-cornered outline keeps showing up wherever people need to name a small triangle.
先想一頂普通的帽子，帽簷整圈平放。現在把帽簷往上折起來固定住，折兩邊或三邊，輪廓就不再是圓的了——它變成一個有角的形狀，一個三角形頂在頭上。這個名字抓住的就是那個折起來、帶著角的樣子。它也解釋了兩件事：為什麼這頂帽子只出現在舊時代軍官和水手的畫像裡，以及為什麼後來凡是要指認一個小三角形的場合，人們都還會借用它的名字。
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