I do have the problem of making all my characters sound alike. I think it's because I get obsessed with telling the story and don't want to get bogged down with "now how would she say this with her accent?" :)
When I was writing a story and I describing body armor that various characters in my story were wearing and I used the term Lorica Segmentata which is a type of body armor worn by the ancient Romans granted I included that because it suited the story and I love the way the armor looks however I don't think alot of people would even know what Lorica Segmentata.
Sometimes anything with little diffused understanding of what the meaning is, you can put an asterick on it and then at the bottom of the page under the regular story line you are creating you will describe it.
I know I'm super late to reply but I think in this case I'd use the term alongside some additional description so that the reader knows what's going on without looking it up (ie ruining the flow of the story)
Does this also work for a character's appereance? I often see readers criticize not having a clear image of a character in their head. But does it matter, in the end of the day, what a character's jawline, their nose or lips look like? No, because it says nothing about them personality-wise. A hairstyle (or their clothing), on the other hand, does say a lot about a character because they actually have control over it. Is a character's hair messy? Styled with a lot of styling cream? Or oiled in an old-fashioned way? Is a character wearing a strict bun or a messy one? Those are the things I describe, because they actually matter to the story. I never even have a full blown picture of my characters in mind myself because I care too little about their appereance to actually think about their dimples and noses. My perspective character's love interest are the only exception I make because when people are in love, they think about dimples and jawlines...
I think it's more like, choose some details to focus on. Like when you imagine them, what details stand out the most? I usually go with 3 and describe those things clearly. E.g. if it's the hair, not just what colour but what variant of that colour, how long, the name of the hairstyle and how it frames or contrasts with their other features. Or if I choose the eyes, the exact colour, shape, size, lash length, but I also spread these details out over a scene rather than dump them into 1 para. Most importantly I use them to reveal character, e.g. class, gender, status, religion etc. Hairstyle is great for revealing, hinting at or planting red herrings about them.
Does using concrete words apply to using metaphorical imagery in a passage? Like: This was going to far, sooner than later the cross needed to fall. Instead of: This was going too far, sooner than later the church needed to fall. Is the symbol of the cross better than the idea of the church?