George Simmers had a post on his blog the other day about the use of facetiousness in writing at the time of the Great War. He included a quote from Pat Barker to the effect that she had not replicated this type of language among the officers in Regeneration as she felt it wouldn’t play well to today’s audience. It certainly seems a bit silly, but I can see that this type of humour is a way of coping with an impossible situation, and I would trust my readers to understand that.
However, even if one is not attempting to write pastiche, the addition of correct slang and speech patterns can be an important factor in characterisation, if hard to replicate accurately. For example, the language in Patrick O’Brian’s Aubrey/Maturin novels is wonderful, with subtle differences between the characters. Of course, I’m speaking of a historical context here, but the point stands for contemporary fiction.
Aside from the OED, which most people’s budgets can’t stretch to, there are a number of slang dictionaries available, of which the most comprehensive has to be Eric Partridge’s – see my list of recommended books. He also produced a number of more specialised slang dictionaries one of which covers Great War slang, The Long Trail, What the British Soldier Sang & Said 1914-18, sadly long out of print. What I found fascinating about that was the number of phrases and words that are still current. For the Georgian and early Victorian periods there is of course The Dictionary of the Vulgar Tongue by Francis Grose, the 1811 edition of which is available as a download from the Gutenberg project. Reading that, I immediately saw where Georgette Heyer got most of her slang. A later Victorian one, which uses Grose as a source, but which also includes many later words, is the Dictionary of Modern Slang, Cant and Vulgar Words (1859) by John Camden Hotton. Sadly this does not seem to be as widely available as it is a treat.