fossilyoudaoicibaDictYouDict[fossil 词源字典]
fossil: [17] Etymologically, a fossil is something ‘dug’ out of the ground. It comes via French fossile from Latin fossilis ‘dug up’, a derivative of the verb fodere ‘dig’. The English adjective originally meant virtually the same as Latin fossilis (‘Seven unmixt fossil Metals are forecited’, Robert Vilvain, Epitome of Essais 1654), and this sense survives in the present-day expression fossil fuel, but the word’s main modern connotation ‘excavated relic of a former life-form’ had begun to emerge by the mid 17th century.
[fossil etymology, fossil origin, 英语词源]
fossil (n.)youdaoicibaDictYouDict
1610s, "any thing dug up;" 1650s (adj.) "obtained by digging" (of coal, salt, etc.), from French fossile (16c.), from Latin fossilis "dug up," from fossus, past participle of fodere "to dig," from PIE root *bhedh- "to dig, pierce."

Restricted noun sense of "geological remains of a plant or animal" is from 1736 (the adjective in the sense "pertaining to fossils" is from 1660s); slang meaning "old person" first recorded 1859. Fossil fuel (1833) preserves the earlier, broader sense.