free rider vs soap

free rider

noun
  • One who obtains benefit from a public good without paying for it directly. 

  • A worker at an open shop who is able to enjoy the benefits negotiated by a union without being a member of the union. 

  • Someone who obtains goods or services legally without paying. 

soap

noun
  • Money, specially when used as a bribe. 

  • sodium pentothal 

  • A soap opera. 

  • Some other substance, often a detergent or another surfactant, able to mix with both oil and water, used for cleaning. 

  • A solid masonry unit or brick reduced in depth or height from standard dimensions. 

  • A metallic salt derived from a fatty acid, commonly used in cleaning products. 

verb
  • To cover, lather or in any other form treat with soap, often as a prank. 

  • To apply soap to in washing. 

  • To be discreet about (a topic). 

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