I am aware that I started a series of posts a while ago. I'll continue that shortly, but I decided to make a few changes to it and in the meantime I've found this very very interesting tool...
Google and some other organisations with too much time and money have put together a digital database archiving millions of books (in fact they think it's 4% of all books ever published). Using this website you can search all those books for a particular word or phrase, and it will display a graph showing you how the frequency of that word has changed from 1800 - 2000.
For example, if you search for "fish pie"...
You can see how everyone was writing about fish pie in the 1940s, then it trailed off, but is starting to increase again. "Blunderbuss", however, has just been going downhill since 1820.
And then you find sudden changes, like the explosion of "pink pyjamas" around 1914.
Fashion designers commonly refer to this event as the "pink pyjama awakening".
Have a go, it's great fun.