afraid vs on edge

afraid

adj
  • Regretful, sorry; expressing a reluctance to face an unpleasant situation. 

  • Impressed with fear or apprehension; in fear. 

  • Worried about, feeling concern for, fearing for (someone or something). 

on edge

prep
  • Tense, nervous; consequently irritable. 

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