already vs once

already

adv
  • Prior to some specified time, either past, present, or future; by this time; previously. 

  • An intensifier used to emphasize impatience or express exasperation. 

  • So soon. 

once

adv
  • Formerly; during some period in the past. 

  • Multiplied by one: indicating that a number is multiplied by one. 

  • One and only one time. 

conj
  • As soon as; when; after. 

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