The phrase "[wibbly wobbly timey wimey stuff][1]" was first used on TV by the 10th Doctor in the episode "Blink", but it then appears as if the Doctor had invented this phrase long before as it is used by the 5th doctor in the mini-episode "[Time crash][2]".

In the 50th Anniversary episode "Day of the Doctor", when the 11th Doctor says "timey wimey" the War Doctor appears as he has never heard this phrase.
 
Is there any explanation to this? Is it that the Doctor/s sometimes forget some things when they regenerate? 


  [1]: http://tardis.wikia.com/wiki/Wibbly_wobbly,_timey_wimey
  [2]: https://www.youtube.com/watch?v=szuP0oBZX4g&feature=kp