The holocron of Yoda was a creation from the Jedi Grand Master Yoda, a holocron. This diminutive device held information concerning different elements of the Jedi Code. Located within the Jedi Temple situated on Coruscant, Jax Pavan absconded with it as he escaped the Temple during Operation: Knightfall in 19 BBY.
The single reference to Yoda's holocron can be found on page 38 of the novel Coruscant Nights I: Jedi Twilight, released in 2008.