The word eager goes back to the French word aigre, meaning sour. In English, it first took on the sense of sharp, biting, or severe. Then it took on the sense of intense or impatient, which developed into the "ready to go!" sense.
Vinegar also goes back to aigre—vin aigre, or sour wine. That's what vinegar is, after all.
“醋”也来自aigre,即vin aigre,酸的酒,也就是醋,别无其它了。
3. OXYGEN
3、氧气
In the 18th century, when scientists discovered oxygen, they thought of it as the element whose main characteristic was its role in producing acids. The word oxygen was formed from Greek roots to mean "acid generating."