Definition of "gibberish"

Such gibberish as children may be heard amusing themselves with.

1850, Nathaniel Hawthorne, chapter 12, in The Scarlet Letter, a Romance, Boston, Mass.: Ticknor, Reed, and Fields

Could it be, after all, that the whole story was true, and the writing on the sherd was not a forgery, or the invention of some crack-brained, long-forgotten individual? And if so, could it be that Leo was the man that She was waiting for - the dead man who was to be born again! Impossible! The whole thing was gibberish! Who ever heard of a man being born again?

1886 October – 1887 January, H[enry] Rider Haggard, She: A History of Adventure, London: Longmans, Green, and Co., published 1887

The Game of Thrones novels were best sellers without fleshed-out Dothraki; the languages in Star Wars, one of the most successful franchises ever, are mostly gibberish, even if Han Solo claims to understand Chewbacca’s bestial warbling.

2022 December 31, Matteo Wong, “Hollywood’s Love Affair With Fictional Languages”, in The Atlantic