"fossil [...] adj. [...] Obtained by digging; found buried in the earth. Now chiefly of fuels and other materials occurring naturally in underground deposits; esp. in FOSSIL FUEL n."
Kaldany, Rashad, Director Oil, Gas, Mining and Chemicals Dept, World Bank (13 December 2006). Global Gas Flaring Reduction: A Time for Action! (PDF). Global Forum on Flaring & Gas Utilization. Paris. Retrieved 9 September 2007.