沙在流＝時間在走
這一組借的是沙漏的功能：看著沙落下，就知道時間在走、還沒到。
noun · B1
A timer made of two rounded glass halves joined by a narrow neck, holding sand that runs slowly from the top half into the bottom one to measure a fixed length of time.
沙漏
核心畫面
One object holds this whole word: two rounded glass halves together at a narrow neck, with sand falling through. Two things about it can be borrowed. The shape - wide, narrow, wide - and the message the falling sand sends: time is passing and you can only wait. Every meaning here takes one of those two.
這個字可以想成一件東西就講完了：兩個圓鼓鼓的玻璃半身，中間被捏成細細的頸，沙從那裡流下去。這件東西身上有兩樣可以借走…更多收起
這個字可以想成一件東西就講完了：兩個圓鼓鼓的玻璃半身，中間被捏成細細的頸，沙從那裡流下去。這件東西身上有兩樣可以借走的東西。一個是形狀——寬、窄、寬。另一個是沙在流時傳出的訊息——時間正在走，你只能等。這個字的每一個意思，都是借走了其中一樣。From the word’s history
The packet's source gives the word as simply hour plus glass: the glass thing that measures an hour. That literal build is still visible in the object, and it explains why small three-minute timers keep the name even though they do not run for an hour.
這份資料的來源說，hourglass 就是 hour 加 glass：量一個小時的玻璃器。這個字面組合到今天還看得出來。也因為名字綁的是那個東西，三分鐘的小沙漏一樣叫 hourglass，並不會因為跑不到一小時就換名字。
Wiktionary 'hourglass' etymology as supplied in this packet: From hour + glass (source_ref kaikki:3f6f69a190036ae4:88167758)
Two branches
中間收窄的形狀
這一組借的不是功能而是外形：寬、窄、寬的那條輪廓線。
noun · B2
Used in the phrase an hourglass figure to describe a body, usually a woman's, whose waist is clearly narrower than the chest and the hips, so that the outline looks like the pinched middle of an hourglass.
沙漏身材