Need help In SC

Dear Angelgabriel,
I'm happy to help.

In English, there are three kinds of conjunctions.
1) Coordinating conjunctions --- and, but, or, etc. ---- join equal parts --- these could join two independent clauses, or two phrases, but not one with the other; we could not use any of these in this sentence.
2) Correlative conjunctions --- both ... and; not ... but; not only ... but also; etc. ---- pairs of words that join equal parts; we also could not use any of these in this sentence.
3) Subordinating conjunctions --- because, since, that, which, etc. ---- these mark the beginning of a dependent clause.
For more info, see:
https://magoosh.com/gmat/2013/gmat-idiom ... junctions/
https://magoosh.com/gmat/2012/run-on-sen ... questions/

There's no magic word we can insert, in the place of "AND", to fix the sentence. We need to re-write:
Either, we could have two independent clauses joined by AND":
Famously uttered by Archimedes, the term "eureka," meant "I have found it" in ancient Greece, AND ever since then, scientists have exclaimed the same word upon making important discoveries.
Or, we could make the first part as a dependent clause. If we use the subordinate conjunction "because", that includes the idea of causation and establishes a sequence, so we don't need the emphatic "then" in the second part:
Because Archimedes famously uttered "eureka," meaning "I have found it", scientists ever since have exclaimed the same word upon making important discoveries.

Does all this make sense?
Mike