heyday
UK[ˈheɪdeɪ]US[ˈheɪdeɪ]
n
The period of a person's or thing's greatest success, popularity, or vigor.
Etymology
The word 'heyday' originated in the late 16th century as an exclamation of joy, surprise, or wonder, recorded as 'heyda'. This interjection is thought to be an alteration of the earlier phrase 'high day', which itself denoted a festive or ecstatic period. The semantic shift from an exclamation to a noun describing a peak period is a classic example of grammaticalization, where a spontaneous expression of a heightened state becomes lexicalized as the name for that state. The modern abstract meaning, referring to the zenith of success or vitality, fully emerged in the 18th century, preserving the core idea of an exalted, celebratory time from its original components.
Analysis
The word is a simplex form. It is an alteration of the archaic expression "high day," where 'high' meant 'exalted, ecstatic, joyful' and 'day' referred to a period of time.
Examples
The 1920s are often considered the heyday of jazz.
The company's heyday was in the 1990s, before the market changed.
In his heyday, he was one of the most formidable athletes in the world.