basilica vs sacellum

basilica

noun
  • A Christian church building having a nave with a semicircular apse, side aisles, a narthex and a clerestory. 

  • A Roman Catholic church or cathedral with basilican status, an honorific status granted by the pope to recognize its historical, architectural, or sacramental importance. 

sacellum

noun
  • A small chapel, as a monument within a church. 

  • In Ancient Rome, a shrine open to the sky, sometimes used for sacrificial purposes, or in honor of the divine. 

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