accelerating vs gradual

accelerating

noun
  • An act of acceleration. 

gradual

noun
  • An antiphon or responsory after the epistle, in the Mass, which was sung on the steps, or while the deacon ascended the steps. 

  • A service book containing the musical portions of the Mass. 

adj
  • Proceeding or advancing by small, slow, regular steps or degrees 

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