https://english.stackexchange.com/questions/305312/where-does-the-sky-is-falling-come-from
Henny Penny, more commonly known in the United States as "Chicken Little" and sometimes as "Chicken Licken", is a folk tale with a moral in the form of a cumulative tale about a chicken who believes the world is coming to an end.
The phrase "The sky is falling!" features prominently in the story, and has passed into the English language as a common idiom indicating a hysterical or mistaken belief that disaster is imminent.