So how do you go about finding/using words for new-er things in ancient Greek? It’s a conundrum, and it’s more a conundrum in Greek than Latin, but here are a few of my working principles:

1. I look at English>Greek dictionaries. Woodhouse, Yonge, Fradersdorff. These usually require trying to think of a 19th century way of expressing something.
2. I look at how Latin, especially contemporary Latin, expresses things, using the English>Latin at Latinitium (Smith and Hall, primarily), as well as the Neo-Latin Lexicon. I then consider what Greek words might correspond to the Latin well, including using a Latin>Greek lexicon.
3. I look at how Modern Greek expresses the idea or term. If it’s a derivation from an ancient word, I reverse engineer the etymology where appropriate.
4. Ask other contemporary speakers of ancient Greek what they are using. I have a few go-to friends who are good for this.
5. In all these steps, I’m trying to figure out
   1. Is there an ancient attested word that could reasonably be extended to represent the new thing?
   2. Is there an obvious neologism that would be transparent to an ancient speaker, and generally conforms to ancient usage?
   3. Does modern Greek and/or contemporary Latin use a loan word or calque, and would the same strategy work for a ‘new’ ancient word?

In all this, my principle is basically “be as linguistically conservative as possible”, because I’m still trying to speak an ancient Greek in a modern context.

Apologies too, I couldn’t resist the title.