Tech-limited metaphors?

Question

In my native language, we sometimes use the expression "to be shot by (Someone)'s eyes", meaning that Someone is staring at you very intently and in an examining, measuring manner, most often trying to find out whether you are lying or not.

While writing my fantasy novel, I used the expression without giving it much thought, but it keeps bugging me, because gunpowder has not been invented/discovered in my setting.

In my specific case the expression is used by a third-person limited narrator, but I'll make the question more generic.

Is it ok to use a metaphor none of the characters would understand because of tech-limitations? (or any other limitation, for that matter)

Answer 1

I think it is extremely important to keep all content of the book including the narrator not have any anachronism. This is unless it's meant for specific effect like comedy, time travel,or some sort of modern reflection,

Keeping the reader emerged in the work is one of the most important parts of creating a good narrative. Any references outside the work shatter this emersion. Writing fiction in another time period gives the author the fun challenge for researching or creating sayings that would correctly fit into the time period. These little details can go a long way towards making your creation feel like a real world, with a lot more lurking past what the reader can "see",

Readers are also smart and will understand saying if they sound familiar. This often gives great space to use that familiarity to instead develop something else. If you instead say "she stared at me like a flork-nork", people will understand it's intense, and now be exited to find out what is a flork-nork in your world

In my work I try to even avoid things like measuring systems, or calendars that would somehow attach my fictional world to real life events.