Depends on various things, 1 Location 2. Time peroid and 3. The class using them. I could give you some ideas of terms used for Britian and Ireland that were around queen victorias time
Some slang by lowerclass would include Brickies (brick layer ) Quakers (worked soup kitchens in irish famine ) (Mutton Shunter) policeman Docker (dock worker) THREE-PENNY UPRIGHT ( a prositute ) Bit Faker (someone who made fake coins ) Bludger (violent criminal) Didikko (person of travelling community) Dipper (Pickpocket) Don (leader or distinguised person ) Flash (something or someone Posh eg flash house) Spike Workhouse , landsharks bloodsuckers(landlords) gentry (gentleman

Upperclass and middle being better educated would be less likely to use slang, When I look at letters written at the time about the famine for example the terms used are straightforward compared to lowerclass slang but terms I've seen are things like the labouring men, The middle men (for landlords) Tendry (tennants)
"It would be impossible adequately to describe the privations which they [the Irish labourer and his family] habitually and silently endure ..."

I think if your looking for earlier good examples of how things were written earlier would be to read a few chapters from books of that era your interested in that focus on class division eg poldark (set in early 18th century) or something like homers oddessy if you want ancient greece, shakespere if you want 1600s etc