historical notes on ecology and evolution
These are Google searches of those terms by year? What is the percentage measure on the y-axis?
Google calls the search term "Darwinism" a 1-gram or unigram and the search term "Intelligent Design" a 2-gram or bigram. If we searched for the bigrams "Intelligent Design" + "intelligent design" only, the y-axis would show this: of all the bigrams contained in their sample of books written in English and published in the United States, what percentage of them are "Intelligent Design" or "intelligent design" added together (yellow line).see: http://books.google.com/ngrams/info