A croissant is quite aptly named. The English and French word can be traced further back to an earlier French word, cressaunt. This is fascinating because it is also the root of the word crescent; croissants were named thus because of their resemblance to a crescent. Both have agricultural origins, but not directly so. Cressaunt came from the earlier term creissant, specifically referring to the "crescent of the moon". This came from a Latin word, which probably was either crescentum, crescens, crescere, or cresco, all of which had to do with "thriving" and growing out of the ground (and the etymon of create). This change is weird, and kind of hard to understand, but I'm sure it makes sense to those superior to you or myself in etymology. Crescere and all its forms are derived from Proto-Indo-European, and the root ker, or "to grow" (for fans of mythology, that's the root of the goddess Ceres). People like colloquialisms about things growing on trees, and next time somebody asks you if money grows on trees, you can simply ask, "Etymologically speaking, croissants do. Why not money?" You're welcome.
Adam Aleksic, a rising sophomore studying linguistics and government at Harvard University, has been described as the internet's sixth most famous etymologist. He also has disturbing interests in politics, vexillology, geography, board games, conlanging, and law.