midsummer (n.)youdaoicibaDictYouDict[midsummer 词源字典]
Old English midsumor, from mid + sumor "summer" (see summer (n.1)). Midsummer Day, as an English quarter-day, was June 24. Astronomically June 21, but traditionally reckoned in Europe on the night of June 23-24.[midsummer etymology, midsummer origin, 英语词源]