As a non-native English speaker, I always wondered why, for example, you say moon, but then you say lunar (same goes for side and lateral, hand and manual and so forth): in some cases, the noun is not the base of the adjective, which derives from the Latin root instead.
What is the reason for this phenomenon?
Let’s not forget that Latin was the language of science and philosophy and nearly all higher learning for hundreds of years. For example, Copernicus wrote his seminal treatise about the heliocentric theory, De revolutionibus orbium coelestium, in Latin. It’s not surprising that many of the technical names for natural phenomena and educated words in general would be derived from Latin.
We see remnants of this today in medicine: the parts of the body are named from the Latin. Your orthopedist will tell you you’ve torn your medial collateral ligament in your knee.