expert vs time-served

expert

adj
  • Extraordinarily capable or knowledgeable. 

  • Characteristic of an expert. 

noun
  • A player ranking just below master. 

  • A person with extensive knowledge or ability in a given subject. 

time-served

adj
  • Having completed an apprenticeship or period of training, thus acquiring skills. 

  • Having completed many years of service. 

How often have the words expert and time-served occurred in a corpus of books? (source: Google Ngram Viewer )