Pronounced PET-ri-kuhr, the noun means the pleasant smell that accompanies the first rain after a dry spell. Two Australian geologists invented petrichor in 1964 after they discovered the scent’s source.
The word is a concoction of the Greek, petros, stone, and ichor, which is a blood that flowed in the veins of the gods and helped keep them immortal.
In this case, during dry spells, many kinds of vegetation give off oils, the ichor, that coat the soil and rocks, the petros, below. When water hits the ground, the oils exude that distinctive, earthy fragrance.
And so, thanks to these two Australians, we can get blood from a stone.