It's fairly frequently that we don't use or mention something that is historically in-period for Fallen London because players would think it's anachronistic. Examples of such things include semi-automatic pistols (definitely a thing you could buy in Europe in 1899). There's one bit in FL where you run into a saxophonist and the only reason that flies is because he's a Devil, and Devils in the FL setting are culturally unstuck in time (even though saxophones had existed for a long time in the period). This phenomenon is a byproduct of the simplified and often incorrect way people conceptualize history.
But one thing that falls under this rule that I am often sad I can't use is the word 'dude' (first attested in English in 1877).
