The story
Popularized by 'Get Yer Ya-Ya's Out!': The Rolling Stones in Concert, an 1970 live album by English rock band the Rolling Stones.
Etymology from Wiktionary, CC BY-SA 4.0.
get one's ya-yas out
Today it means: To behave in a wild and carefree manner, so as to use up excess energy or exuberance. Full definition →