Of course, that can be taken too far; which among us has not rolled our eyes (if not literally, then mentally) when some member of the Historical Police has said that something could not POSSIBLY be because it didn’t exist until a year later.
To which I always say, “It’s fiction. Deal with it.”
(That doesn’t excuse just missing or poor research, such as when a Duke is called My Lord instead of Your Grace, or if a divorce is regarded as blithely in a Regency romance as it is today.)
But there are circumstances, certainly, where things existed prior to being documented. For example, language. Many of us Regency authors own Captain Francis Grose’s 1811 Dictionary of the Vulgar Tongue (I have two copies, myself), and it’s fun to skim through and realize many words were in existence then that you wouldn’t have thought.
And just this week comes news that the Oxford English Dictionary has added new words to its definitive tome: he words “OMG,” “LOL” and “FYI,” as well as ♥, as in “I ♥ NYC.”
The last one is just nuts! It’s the first time a symbol has been defined as a word. But certainly it has been around for much longer than its acknowledgment within the OED, and one can surmise that certain words and phrases were around a lot longer in Regency times than documentation allows for.
What words jar you from a story? What words surprised you by being extant at the time? What word do you think the OED should add next–or never allow within its pages?