The term "carbon footprint" derives from the concept of an "ecological footprint," presented in a 1992 dissertation by Mathis Wackernagel under the supervision of his Canadian professor, William Rees. The usage narrows the focus specifically to carbon emissions produced by a given activity. The term gained much wider currency thanks to advertising and promotion in the mid-2000s by BP, the large U.K.-based oil company.
In 2008 the late William Safire, a noted language authority, traced "footprint" usage to 1965, referring originally to spacecraft landings. Wackernagel and Rees later published a book about humans' ecological footprint, and Wackernagel founded and still leads the Basel-based Global Footprint Network, which promotes sustainable development approaches.