A little side-project (I've got a few of these, it seems) of mine is compiling a dictionary of seventeenth-century slang. This is partly for its own sake (it's interesting as heck) and partly for research purposes. Not, though, as one might imagine, for use as a writing tool in and of itself, but for context.
Too much period folderol, and you run the risk of, at best, showcasing research for its own sake ( the "I've read it and made notes dammit, so I'm going to use it" school of writing) or, and perhaps worse, making the text all but unintelligible to anyone other than period experts and the worryingly patient.
What the language specific to any point in time gives you, though, is a sense not just of the way words were used, but of the contexts in which slang developed. You get a peek into the crimes and the prejudices, the working lives and the enthusiasms, the obsessions and the mindsets of the age. You also get a feel for the speed of language mutation. In the 21st century, slang burns itself out fast: instant dissemination ensures that the language of a year loses its novelty fast, and we, addicted to above all the new, crave the fresh.
Language moved slower before social media, before TV and almost universal ability to read, before radio, before the ubiquity of the printed word. Some of the slang from the Restoration era (and earlier) is still around, and a surprising amount of contemporary insulting and denigrating wordage has its roots in the age. The connections, the shared associations, and the abiding preoccupations link us, through slang - often the unfiltered and thus a truer picture of the time - to the past.
My compilation method is pretty basic and long-winded. It involves a copy of Jonathan Green's Dictionary of Slang, a pen and a ledger, and some time. It means reading the dictionary alphabetically and writing down longhand entries that are specific to the 17th century.
Yeah, I know.
What you get, though - partly through the exercise and partly through the time it takes to make notes on each - is a better sense of the period. It's hugely useful. And yep, the occasional word might make its way into a story, but better and handier than that, the feeling for the history is magnified. As someone who's written one seventeenth century-set novel (and with others on the horizon) any tactic that gets you back to the past is to be welcomed.
By way of example, a few snippets from the early pages. These are my notes but the work derives from Green's Dictionary of Slang - a book that's pretty much essential for anyone with a love of words. Mine's an old edition picked up in a branch of The Works, though there's a three-volume set from 2010 that's a thing of beauty.
an admiral of the narrow seas: a drunk who vomits over their neighbour at table
an affidavit man: a professional witness - someone who will swear to anything
allicholy: melancholy through drink
angler: a thief who uses a hook and a pole
arse-worm: a small person
badger-legged: having one leg shorter than the other
a barleybun gentleman: a rich man who chooses to live poorly
barnacle: a toady, a hanger-on
basket-scrambler: someone who lives on charity
bawcock: a fine fellow
beanbelly: someone from Leicestershire
beau trap: either a fixed card game, or else a badly-laid paving stone, the kind that would splash one's finery
bingo: brandy (a bingo-boy is a man who loves brandy, and a bingo-mort a woman likewise)
Halfway through the Bs and you get a feel for a world obsessed with sex, food, vomiting, illness, thievery, swindles and cons, insults, mockery, taking the mickey out of rustics, and so on. Maybe not that much has changed in the last 350 years or so...