Origin of heydayearlier heyda probably from (or akin to) German and Danish heida, Dutch heidaar, hey there!: see hey
Origin of heydayMiddle English hei dai, full daylight, well on in the day from hei, high + dai, day
Origin of heydayPerhaps alteration of heyda exclamation of pleasure probably alteration of Middle English hey hey
- A lively greeting.
heyday - Computer Definition
An earlier time period in which something was very popular. For example, "the CP/M operating system had its heyday in the 1980s." Pronounced "hay-day."