We have an electronic keyboard that my son calls "the companio" (kumPANyo). I've heard him say "piano" about the real piano at church, but although my partner usually refers to the keyboard as a "piano" my son seems to think it needs a different word. Maybe it's a combination of "computer" and "piano".
A "scotch" is a small amount. I don't know where he got that. At first it seemed to refer to a small thing of a certain shape: "I'm putting a few scotches of mustard on my sandwich." or (describing the lighting of a match) "Daddy made a scotch of fire on a stick." But now it seems to mean a small amount of anything: "I want to watch TV! Please, just one scotch?"
The first meal of the day was "bexxiff" for a long time and is now "brexxiff."
When he farts, he says, "There's a guff going by!" This is a reference to Oh, the Thinks You Can Think!
by Dr. Seuss. If you look at the picture of the guff, you can see how he made the association!