
The post made me think of just how much we rely on certain vocabularies to establish voice. Characters have their own way of saying things. Speech patterns and words establish character and narrative voice, so the usage of words is absolutely essential.
As writers, we need to know words. Lots of words. Huge Mack truckloads of words, but that's not all. We need to know the permutations and histories. The meanings of words changes over time. Yes, a simple online dictionary can give a list of current definitions, maybe even suggest slang usage, but most of those won't tell the etymology of the word. There are a couple of online etymology sources, but none of those compare to the definitive source for the English language: the Oxford English Dictionary (OED).
There is only one OED. Oxford University Press puts out many dictionaries, but only one of which is the OED. Nothing compares to how thorough the OED is in chronicling the language. In print form it is over 20 volumes, and it does much much more than simply give definitions. This is a resource which peels back the layers of the language to show off its roots. It is now available online, so writers need not devote shelf space (or backpack space) to the 20+ volume set. It is accessible anywhere in the world.
Now, it's not free. In fact, its cost is prohibitive for most writers to purchase on their own. However, most university and public libraries purchase access to the OED, so it may be freely available via library web portal. Go forth and explore the wonderful language. Bonus points for those who knew the picture was of a noggin.