yada yada yada
Chiefly US Probably influenced by (or perhaps an alteration of) yatter or yatata; perhaps onomatopoeic of blather ; or perhaps derived from the Norwegian expression "jada, jada" which has a similar pronunciation and interpretation. Sometimes popularly attributed to Yiddish, but this is dismissed by etymologists.
"Yatter, yatter" is British (specifically Scots) English for "continuous chatter, rambling and persistent talk". S. R. Crockett, The Men of the Moss-Hags (1895) xxix: "The woman's yatter, yatter easily vexed me."  Yadder is a Cumberland word meaning "to talk incessantly; to chatter". 
Various variant forms appear in the US 1940s–60s; for example, the 1947 American musical Allegro by Oscar Hammerstein II and Richard Rodgers contains a song called “Yatata, Yatata, Yatata,” about cocktail party chatter; see talk page for additional citations.
The phrase "yadda yadda" was first popularized by the comedian Lenny Bruce in his standup bit "Father Flotsky's Triumph," the closing track on his 1961 album "Lenny Bruce - American." It gained renewed popularity in the US in the late 1990s on the television show Seinfeld, where it appears as a catchphrase, initially in Season 8, Episode 19, entitled “The Yada Yada”, originally aired on April 24, 1997, which centers around the phrase (in the duplicative “yada yada” form).
Normally used mid-sentence.
- They’re no good, the lot of them—Yaddeyahdah—They're animals! —Lenny Bruce
- 1981, The Washington Post, January 5th, 1981, page B1:
- I’m talking country codes, asbestos firewalls, yada yada yada.
- (and so on): and so forth, and so on, and yada yada, and yadda yadda, etc., etcetera, blah blah blah
- ^ OED
- ^ OED
- ^ “yada yada yada”, in Merriam–Webster Online Dictionary, (Please provide a date or year).
- ^ Dictionary of the Scots Language
- ^ Wright, Joseph, The English Dialect Dictionary (1898), London: H. Frowde; New York, G.P. Putnam's Sons
- ^ On this date, Seinfeld made “Yada Yada Yada” a catchphrase (but didn’t coin it), This Day in Quotes, April 24, 2010