inroad vs protection

inroad

noun
  • An advance into enemy territory, an attempted invasion; an encroachment, an incursion. 

  • Often followed by in, into, or on: initial progress made toward accomplishing a goal or solving a problem. 

protection

noun
  • Coverage. 

  • A means of keeping or remaining safe. 

  • The process of keeping (something or someone) safe. 

  • The state of being safe. 

  • An instance of a security token associated with a resource (such as a file). 

  • Restrictions on foreign competitors which limit their ability to compete with domestic producers of goods or services. 

  • A means, such as a condom, of preventing pregnancy or sexually transmitted disease. 

  • Immunity from harm, obtained by illegal payments, as bribery or extortion. 

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