• n. 全盛期
• int. 嘿！（表喜悦或惊奇等）

来自感叹词heyda,表示惊叹，惊讶，后拼写俗化为day.引申词义盛世，全盛时期。

heyday

heyday: [16] Etymologically, the -day of heyday has no connection with the English noun day, although it has come to resemble it over the centuries. Nor is hey- related to hay. Originally the word was heyda, an exclamation roughly equivalent to modern English hurrah. Probably it was just an extension of hey, modelled partly on Low German heida ‘hurrah’. Its earliest noun use (first recorded in the 1590s) was in the sense ‘state of exultation’; the influence of the day-like second syllable did not make itself felt until the mid-18th century, when the modern sense ‘period of greatest success’ began to emerge.

heyday (n.)

late 16c., alteration of heyda (1520s), exclamation of playfulness or surprise, something like Modern English hurrah, apparently an extended form of Middle English interjection hey or hei (see hey). Modern sense of "stage of greatest vigor" first recorded 1751, which altered the spelling on model of day, with which this word apparently has no etymological connection.