mal- vs ob-

mal-

prefix
  • incorrect 

  • incomplete, unfinished 

  • unintentional, mistaken, accidental 

  • unpleasant 

  • poorly, deficiently 

  • not 

  • unhealthy, harmful 

  • evil 

ob-

prefix
  • Of a reversed shape. 

  • Obligatory; prepended to the name of a topic being mentioned to avoid accusations of being off-topic. 

  • Against; facing; a combining prefix found in verbs of Latin origin. 

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