Green’s Dictionary of Slang

predictable, repetitive, essentially meaningless chatter; thus attrib., talkative.

1946		E. Wilson Pikes Peek or Bust 1357: For my B[eautiful]. W[ife]. is the yatatayatata type, whose irresistible charm even I, a columnist drugged on charm, am unable to resist.
1993		M. Myers et al. Wayne’s World II [film script] Yada yadda yadda Wayne yadda yadda yadda Garth yadda yadda yadda Aerosmith.
1997–2001		Online Sl. Dict. 🌐 yada 1. et cetera. (‘We went to the mall, saw some friends, yada yada yada, the usual stuff.’).
1999		R.G. Barrett Wind & Monkey (2013) [ebook] Les tuned the radio to some yadda-yadda talkback station.
1999		USA Today 23 Dec. 04D: While Buffy hasn’t yet had a word achieve the breakout status of Seinfeld’s ‘yada, yada,’ or All in the Family’s ‘meathead,’ it is a rich source.
2000		F. Kellerman Stalker (2001) 360: ‘Yadda, yadda, yadda.’ Carolyn arose from her seat.
2002		J. Lerner You Got Nothing Coming 154: Timmy swears up and down and sideways that he didn’t snitch on anyone, would never try to get nobody crossed out and yada, yada, yada until the boys get completely nauseated.
2006		N.Y. Times 19 June E1/1: They nicely balance an interest in Eudora Welty with the obligatory yadda-yadda about Prada.
2012		(con. 1954) ‘Jack Tunney’ Tomato Can Comeback [ebook] We’re completely impartial and just report the news, that’s all. Yada yada yada.
2013		T. Robinson Hard Bounce [ebook] ‘Yadda, yadda, yadda.’ She opened and closed her hand in my face with each ‘Yadda’.
2021		‘Aidan Truhen’ Seven Demons 81: All hope abandon yada yada.
2023		M. Herron Secret Hours 83: ‘Oh, my loyalties lie entirely with the PM—’ ‘And yada yada yada’.