The Free On-line Dictionary of Computing (30 December 2018):

palmtop
Hand-held Personal Computer
H/PC
pocket computer

    (Or "pocket computer", "Hand-held Personal
   Computer", H/PC) A small general-purpose, programmable,
   battery-powered computer cabable of handling both numbers and
   text (in contrast to most pocket calculators) which can be
   operated comfortably while held in one hand.  A palmtop is
   usually loaded with an operating system such as Windows
   CE.  Data can be transferred between the palmtop and a
   desktop PC.

   A palmtop is very similar to a Personal Digital Assistant
   though a palmptop may have a larger keyboard and more RAM
   and is possibly more general purpose in concept, if not in
   practise.

   The Psion Organiser is one of the best known examples.  [Was
   it the first?]

   (1998-04-19)