What does dejavu mean?
Deja vu is the experience of feeling sure that one has already witnessed or experienced a current situation, even though the exact circumstances of the previous encounter are uncertain and were perhaps imagined.
Yogi Berra was the guy who said, "It's deja vu all over again," which was intentionally comical. By putting it that way he's managed to say the same thing twice -- and in grammar that's a tautology.
Feeling you've done something before..