offer vs volunteer

offer

verb
  • To propose or express one's willingness (to do something). 

  • To present in words; to proffer; to make a proposal of; to suggest. 

  • To put in opposition to; to manifest in an offensive way; to threaten. 

  • To happen, to present itself. 

  • To place at someone’s disposal; to present (something) to be either accepted or turned down. 

  • To place (something) in a position where it can be added to an existing mechanical assembly. 

  • To present (something) to God or gods as a gesture of worship, or for a sacrifice. 

  • To bid, as a price, reward, or wages. 

noun
  • An invitation to enter into a binding contract communicated to another party which contains terms sufficiently definite to create an enforceable contract if the other party accepts the invitation. 

  • Something put forth, bid, proffered or tendered. 

  • A proposal that has been made. 

volunteer

verb
  • To do or offer to do something voluntarily. 

  • To offer, usually unprompted. 

  • To grow without human sowing or intentional cultivation. 

  • To enlist oneself as a volunteer. 

  • To offer the services of (someone else) to do something. 

noun
  • A plant that grows spontaneously, without being cultivated on purpose; see volunteer plant in Wikipedia. 

  • A voluntary member of the organized militia of a country, as distinguished from a regular or member of the standing army. 

  • One who enters into military service voluntarily (but who, when in service, is subject to discipline and regulations like other soldiers), as opposed to a conscript. 

  • A native or resident of the American state of Tennessee. 

  • One who enters into, or offers themself for, any service of their own free will, especially when done without pay. 

  • A person who acts out of their own will without a legal obligation, such as a donor. 

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