- upsilon (n.)
[upsilon 词源字典]
- 20th letter of the Greek alphabet, 1640s, from Greek u psilon, literally "a mere (or bare) 'u;' " so called in later Greek in reference to its sound. The exact reason is variously explained, but it seems to have had something to do with distinguishing it from diphthongs.[upsilon etymology, upsilon origin, 英语词源]