Polish word list 1:
  This version of Polish dictionary was compiled
  by Włodzimierz Macewicz <W.Macewicz@ia.pw.edu.pl>

  Build: 02.01.1999
  by W.Macewicz <W.Macewicz@ia.pw.edu.pl>

  The dictionary has over 440K words and it needs about 5MB
  of disc space. It includes almost all the words from
  the Mazovia dictionary

  ftp://iapw.ia.pw.edu.pl/sys/pub/slownik

Polish word list 2:
  Based on aspell dictionary word list:  http://www.kurnik.pl/slownik/
  Compiled by Michal Joachimczak <guhru (at) gabri.pl>, June 2005

Word Frequencies obtained from: https://github.com/openboard-team/openboard/blob/master/dictionaries/pl_wordlist.combined.gz