offering vs offertory

offering

noun
  • A contribution given at a religious service. 

  • Something put forth, bid, proffered or tendered, such as for sale 

  • That which has been offered; a sacrifice. 

  • The act by which something is offered. 

  • An oblation or presentation made as a religious act. 

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 offering and offertory occurred in a corpus of books? (source: Google Ngram Viewer )