immobilization vs obstacle

immobilization

noun
  • The act or process of preventing a thing from moving. 

  • The process in which organic soil matter is decomposed and absorbed by microorganisms, and thus not available to plants. 

obstacle

noun
  • Something that impedes, stands in the way of, or holds up progress, either physically or figuratively 

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