look at vs onlook

look at

verb
  • To observe or watch (something). 

  • to face (to be presented or confronted with; to have in prospect) 

  • To consider. 

  • To study (something) visually. 

onlook

verb
  • To look on or look at; watch; observe; view; regard. 

noun
  • The act of looking on (something); observation. 

  • One's perspective or outlook. 

  • That which is looked at, regarded, or considered. 

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