probationer vs rookie

probationer

noun
  • One who is on probation. 

  • One who is licensed to preach, but not ordained to a pastorate. 

  • A chorister in their training period before full admission to a choir, whether or not that period is probationary. 

rookie

noun
  • An inexperienced recruit, especially in the police or armed forces. 

  • A type of firecracker, used by farmers to scare rooks. 

  • A novice. 

  • An athlete either new to the sport or to a team or in his first year of professional competition, especially said of baseball, basketball, hockey and American football players. 

adj
  • non-professional; amateur 

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