One way to hold this word: stand on the ground and look up past the clouds. Weather stops somewhere above them, and beyond that is a calm, thin layer of air that begins around ten up. It is far enough away that you will never stand in it, and high enough that reaching it counts as an achievement. Both meanings of the word live at that height — one as real air, one as a way of saying how high a number has gone.
From French stratosphere, coined by the meteorologist Leon Teisserenc de Bort, from strato- (layer) plus -sphere: the layered shell of air, air that sits in still layers instead of mixing.
來自法文 stratosphère，是氣象學家 Léon Teisserenc de Bort 造的字，由 strato-（層）加 -sphere（圈、球層）組成，字面就是「分層的那一圈空氣」。這條線索正好對上它的性格：這裡的空氣安靜地分層待著，不太上下對流，所以飛機在這裡飛得穩。
Wiktionary entry supplied in this batch's evidence packet (source_ref kaikki:3f6f69a190036ae4:1025079290)
Two branches
真正的那一層空氣
這一族就是核心畫面本身：一個看得到高度、量得出厚度的真實地方。
noun · B2
Used as 'the stratosphere': the layer of air around the Earth from about 10 to 50 kilometres up, sitting above the layer where clouds and weather form. In it the air gets warmer as you go higher, because the ozone there takes in sunlight.
平流層
借那個高度來說數字
把核心畫面的「高度」搬到看不見的東西上：價格、名氣、地位。既然那一層遠在雲層之上，說某個數字飛進去了，就是說它已經離常態很遠。
noun · C1
A very high level, price, amount or position — so high that it is far above the usual range. It is used in the singular, almost always as 'the stratosphere', and often after a verb of rising.
高得離譜的程度