oblation vs offertory

oblation

noun
  • The offering of worship, thanks etc. to a deity. 

  • A deed or gift offered charitably. 

offertory

noun
  • A prayer said or sung as an anthem while offerings of bread and wine are placed on the altar during the Roman Catholic Mass or the Anglican Communion service. 

  • A linen or silken cloth anciently used in various ceremonies connected with the administration of the Eucharist. 

  • The part of the Eucharist service when offerings of bread and wine are placed on the altar and when any collection is taken; also, the money or other things collected. 

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