heyday 1
/hay"day'/ , n.
1. the stage or period of greatest vigor, strength, success, etc.; prime: the heyday of the vaudeville stars.
2. Archaic. high spirits.
Also, heydey .
[ 1580-90; var. of HIGH DAY, appar. by confusion with HEYDAY 2 ]
heyday 2
/hay"day/ , interj. Archaic.
(used as an exclamation of cheerfulness, surprise, wonder, etc.)
[ 1520-30; rhyming compound based on HEY; r. heyda hei da hey there ]