dithers vs neurasthenia

dithers

noun
  • The creeps; a feeling of fear or anxiety. 

neurasthenia

noun
  • An ill-defined medical condition characterized by lassitude, fatigue, headache, and irritability, associated chiefly with emotional disturbance. 

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