facilitation vs stumbling block

facilitation

noun
  • The process of synapses becoming more capable of transmitting the same type of signal each time certain types of sensory signals pass through sequences of these synapses. 

  • The act of facilitating or making easy. 

stumbling block

noun
  • A hindrance, obstacle or impediment; an opportunity for error. 

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