animus vs bitterness

animus

noun
  • A feeling of enmity, animosity or ill will. 

  • The masculine aspect of the feminine psyche or personality. 

  • The basic impulses and instincts which govern one's actions. 

bitterness

noun
  • The quality of eliciting a bitter, humiliating or harsh feeling. 

  • The quality of having a bitter taste. 

  • Harsh cold. 

  • The quality of feeling bitter; acrimony, resentment; the quality of exhibiting such feelings. 

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