Petrichor is a pleasant word for a pleasant thing: the earthy aroma of rain on soil. The term was coined in a 1964 Nature article by Australian scientist Richard Thomas, who had studied the phenomenon for years. He derived the word from Ancient Greek petra, meaning "rock", and ichor, which was the mythological blood of the gods (the idea was that petrichor is the "essence" of stone, like ichor is the essence of the gods). Before the Nature article, people just referred to petrichor as "argillaceous odour". It was also previously described in Uttar Pradesh, India, as matti ka attar, or "earth perfume", which I think is a way cooler name. Both petra and ichor are of unknown, possibly Pre-Greek origin. Usage of the term peaked in 1975, decreased until 1995, and has been repopularized since.
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.