The late 18th century is strange enough. They were more formal in some ways, reserved when it came to first names, for instance. And they were totally willing to be profane, too. It is a strange blend to me. Part of it is the USA. A guy like Archie would have used the c-word, not as a particularly shocking and dreadful curse, but simply as a noun. To me that is a total shock. (some small quavering part of me is saying 'I thought you were a nice boy!')
So, while staying away from that, I have tried to use their words and constructions as a sort of spice. I hope to give a feeling of the past, without going crazy with it, and making it all feel too far away.
So now I am attempting the exact lifetime of Shakespeare. And trying to do the same thing. As Charlie has said, we are fortunate. Plenty of words that we think of as 'modern' were used by him. The example she uses is 'punk.' I found 'suburb' as well, which amuses me. (Shakespeare and Marlowe were born the same year, and Mr S is a lot easier to find stuff out about.)
I have gotten myself a concordance of Shakespeare's works. I can punch a word in and find out if he used it. If he did, I can justify having Marlowe use it too. I am trying to do the spice thing. I hope it works. They are so strange, at once far and near, modern, and so long-gone. We view them through wavering light.
The C-word, if you are curious, is right there in Marlowe's translation of Ovid. (Kit never promised to be a good boy-- and I have my doubts about Ovid.)