lastborn vs runt of the litter

lastborn

noun
  • The youngest child of a family. 

  • The youngest member of any company or organization. 

adj
  • Born last in a family; youngest in a the family. 

  • Younger than anyone else in a group. 

runt of the litter

noun
  • the smallest and weakest person in a group, especially a group of siblings 

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