ball of fire vs sturdy

ball of fire

noun
  • A person who is especially hard-working, high-achieving, ambitious, or active. 

sturdy

adj
  • Resolute, in a good sense; or firm, unyielding quality. 

  • Of firm build; stiff; stout; strong. 

  • Solid in structure or person. 

noun
  • A disease caused by a coenurus infestation in the brain of an animal, especially a sheep or canid; coenurosis. 

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