Of course you get odd surprises sometimes - for example Joe Gargery in Great Expectations describing something as "cool" meaning good.

And at best the dictionaries only give you the earliest date something appears in print, which may be long after it's in common use.

Moeover it's not just the vocabulary, it's the way that the words were strung together into phrases and sentences. Imagine using a dictionary as the only guide for a future historical novelist setting a story in today, in which you had a range of people from different sections of our multicultural society interacting...