hebrew - Why the Sanhedrin has a greek name?

This bothers me since a long time. The biggest Jewish halachic authority, arguably, the peak of the Torah world which can be ever imagined, which has its most basic definitions in the Chumash (70 sages & Moshe Rabbeinu) has no official Hebrew name, rather a Greek name is used and is the name of a Talmudic tractate (the only tractate name which is not expressed in a Semitic language). Rather, it is expressed in the language of the Greeks, which culture is symbolic in standing against Torah philosophy.

Is it known at least when the term was started to use? And maybe: why was introduced?

For those who are unfamiliar with the idea that the word "sanhedrin" originates from Greek, see this link. The word "sanhedrin" comes from the Greek word συνέδριον (sunhedrion) which means "sitting together."