Petrichor

Petrichor  was, as defined by Idris, the smell of dust after rain. Idris used the word "Petrichor" as part of the key to open a back-up TARDIS control, which she gave to Rory through a telepathic link. (DW: The Doctor's Wife)

Petrichor was also the name of a fragrance for which Amy Pond posed as a model in an advertisement. Its slogan was "For the girl who's tired of waiting." This modelling job with Petrichor apparently made her rather famous. (DW: Closing Time)

Real world
The word "petrichor" was coined in 1964 in an article published in the magazine Nature. This means a word used as a major plot element in a Doctor Who episode did not actually exist when Doctor Who first went on the air in 1963.