I believe the term was coined at PARC and was to distinguish between a
time-sharing system and a computer which was “yours” when you put your disk
pack on it and sat in the room where you were. Thus the Alto and Dorados were
personal as they melded to their user, when being used by that user,
I don't think that portrayal of Xerox's view on the mouse is correct. Much of
Interlisp and all of Smalltalk was mouse-based and Interlisp was never designed
for (only) use by youth.
Trackpads are fine except for detail work. Touchscreens are bound by touch
targets needing to be finger-sized.
