A wizard may refer to his spells by a complex old language, a scientist may insist on proper terminology for chemicals, an engineer may mix salty language with long strings of description. A character may also handle context and immediate situations differently. Thus a scientist may well use long scientific terms constantly - much to the annoyance of others. Someone may use slang terms inappropriately, confusing people used to more formal references. Grab one of the handy slang dictionaries available at bookstores or online, and you may be amazed what words used to mean and what phrases vanished.
People are also very efficient creatures.
We like to have concise words, and over time we'll create them as needed. In creating terms in your stories, ask yourself how terms may have changed over time - or be preserved. A tradition-bound culture may use archaic references, a culture with a lot of immigration may adapt a rainbow of foreign words quickly. If its new, there may be very few terms - and those may be quite technical. How important is preserving the original name - If it's vital for some reason that a technology be referred to very specifically, words for it may not have changed or changed much.