out of the ordinary vs unfrequent

out of the ordinary

prep
  • Unusual or exceptional, especially for the better (often used in the negative). 

unfrequent

verb
  • To stop frequenting; cease to frequent. 

adj
  • Not frequent; not common; not happening often; infrequent. 

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