220: petrichor Jul 16, 2015

There are a lot of commonly unknown words, usually either very old or very new. The smell after it rains is generally a favorite one, but the word for it was only invented in the 1960's, 'petrichor'. This word is a blend of 'petro-' which means ‘relating to rocks', as the smell is believed to be caused by a liquid mixture of organic compounds that collects in the ground, and 'ichor'.