出典:Wiktionary
出典:『Wiktionary』 (2026/03/11 01:28 UTC 版)
Late 16th century, from earlier heyda (1520s), as exclamation – compare hey, hei. Sense “period of success, vigor” is a respelling as heyday based on unrelated day (as “period of time”) – compare day in the sun.
heyday
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