lightening vs maintenance

lightening

noun
  • The removal of cargo (especially crude oil) from a vessel in order to reduce its draft 

  • The sensation caused by the descent of the uterus into the pelvic cavity before the onset of labour 

  • The act or result of making something light or lighter. 

maintenance

noun
  • The natural process which keeps an organism alive. 

  • Child support. 

  • Actions performed to keep some machine or system functioning or in service. 

  • A tort and (in some jurisdictions) an offence committed when a third party who does not have a bona fide interest in a lawsuit provides help or acquires an interest to a litigant's lawsuit. 

  • Alimony, a periodical payment or a lump sum made or ordered to be made to a spouse after a divorce. 

  • Money required or spent to provide for the needs of a person or a family. 

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