at all vs once

at all

adv
  • Indicating degree, quantity or frequency greater than zero: to the slightest degree, in any way, at any time or in any circumstance. 

once

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

  • One and only one time. 

  • Formerly; during some period in the past. 

conj
  • As soon as; when; after. 

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