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A
The pleasant, distinctive smell that accompanies the first rain after a long dry period — earthy, sweet, and immediately recognisable.
— OED, 1964
B
Named by scientists I.J. Bear and R.G. Thomas in a 1964 paper in the journal Nature, combining the Greek petra (stone) and ichor (divine fluid).
— Nature, vol. 201
C
The scent is primarily produced by geosmin, a compound released by soil-dwelling actinomycete bacteria when disturbed by rain.
— Chemistry of Rain
D
Also contributed to by plant oils secreted during dry periods, which accumulate in soil and rocks before being released as vapour on contact with water.
— Australian CSIRO, 1964
E
The word briefly appeared as a contestant answer in a 1977 episode of Mastermind, the first time it had been used on British television.
— BBC Archive reference