During a 4 hour hike last Sunday I was talking to a man with Greek and German background. I don't remember at all what we were talking about and it doesn't matter. What does matter is that I ended the sentence with "yada yada yada".
He stopped me short and said, "I know what that means and I hear the American's saying this all the time but where does it come from?"
I immediately told him it must be Yiddish. I didn't know if it actually was Yiddish but we have many phrases and words absorbed into mainstream American English that contain Yiddish words. Bagel, glitch, klutz, kosher, nosh, schlep and schmooze, to name a few. But when I had a few minutes to research the phrase I discovered I was completely wrong.
Actually many people think this comes from Yiddish but that idea was proven wrong by etymologists. The earliest place it was found was from an advertisement in August 1948 "Yatata...yatata...the talk is all about Chatterbox...". From there is was seen years later in the 1970s in a song Yada Yada La Scala. But the place most of us have heard this from is the sitcom Seinfeld season 8 episode 19.
Here are a few clips that demonstrate the use, watch till the end (man do I miss watching Seinfeld!):