To a spin around the web. Seems many folks think yad(d)a was invented for the Seinfeld show, but some trace it back to Lenny Bruce. I remember it being used in a David Frye record about Watergate back in the early '70s where the Ron Steiger prisoner character taunts the warden with a cry of "Yadda yadda Warden!" I looked in Harkavy's Yiddish-English-Hebrew Dictionary and found an entry for yaden 'to vex'. That would mean that yade could be an imperative form. A possible connection, not. Whatever.