communal vs grassroots

communal

adj
  • pertaining to a community 

  • shared by a community; public 

  • defined by religious ideas; based on religion 

grassroots

adj
  • Of, or relating to people or society at the local level, particularly in politics, social movements, etc.; of the grass roots. 

How often have the words communal and grassroots occurred in a corpus of books? (source: Google Ngram Viewer )