とうのむかし
a long time ago; long ago
Also written 疾うの昔、当の昔、遠の昔
Expression, Noun
こいつがそんな玉たまじゃないことなんてとうの昔むかしに解わかっていたからさ。
That's because, you see, I've known he isn't that sort of person from a long time back.