It's not really a matter of copying other people. It's a matter of the fundamental bones of storytelling -- structure. And in SFF, of people drawing from the same wells of science, suspense structure, movies, cultural myths and folklore, past classic literature taught to them in school, children's literature used in school, oral traditions (campfire tales, festival celebrations, etc.) We think in terms of stories, we use anecdotes and allegories to communicate. That's how you can know what a maguffin is without knowing what it was called -- you've been immersed in it since you were a kid and introduced to mystery tales.
Originality is subjective at best and superfluous most of the time, not just in "popular" fiction, but all fiction. It's not a big factor in the emotional power of a story and how authors play with emotional power in a story is what connects us -- or doesn't -- to a story. There is nothing original in The Lord of the Rings or Catcher in the Rye or Dune or Great Expectations. But those stories had an impact for many people, not in comparison to other novels but in and of themselves, sometimes due to the culture of the times they are in and sometimes beyond that.
And because we are so immersed in it, you will not be able to escape the label of unoriginality either. You can avoid whatever phrases you want, someone will still say that you are copying from something else that they like or know of, especially in fantasy fiction/secondary world fantasy fiction. And it likely will be something you haven't even read. Because humans make patterns -- that's part of the experience of stories -- and because how we structure fundamental components is largely universal.
Trope means a repeated motif, phrase or symbol, primarily in music, and that was its original meaning. Essentially, a trope was a thematic element repeated to reinforce the themes or atmosphere of a work, to give it structure and form. "Winter is coming" is a trope in A Song of Ice and Fire.
But people started using trope in a second meaning in regards to storytelling, as something used as a common element across many fictional works, regularly found -- boy meets girl, etc. And that then morphed into a third meaning for the word, as a synonym for cliche -- an oft used, inferior and tired element. Both the second and the third meanings are regularly bandied about in SFF, particularly fantasy on the third meaning, which to my mind is kind of pointless. I think if an author wants to try to avoid any cliche/trope in their work, they are certainly welcome to try it. And then they will have to deal with readers who do not think that they did so. As the veteran of many conversations about whether so and so ripped off so and so, I can promise you that will happen.
In short, you cannot reinvent the wheel. And stories are much older than wheels. But yeah, I second TV Tropes if you are trying to ward off tropes in the second or third meanings of the word with regards to fiction. It will probably cause you despair about that idea, but you can enjoy matching your favorite stories to the various entries.
