answer:I think one problem with the Ngram viewer is that in its basic form such as in the webapp, it is only possible to compare frequency over time. Without being able to examine the context in which the word frequencies rise and fall, it is impossible to draw any conclusions about the cultural trends – it’s useful as a complementary tool for (dis)confirming hypotheses one already has, but it’s extremely difficult to draw sound hypotheses from only this data. Using the data with a dedicated concordancer like Xaira or AntConc (both free) would allow much deeper analysis of the datasets. Unfortunately, the data does not seem to be compatible with them. I think the problem is one of copyright.