One of the mysteries of the English language finally explained.
Definition of fossilia in US English:
fossilia
noun
rareTreated as plural. Fossils. Originally: †mineral substances found in the earth, especially (in Linnaeus's system) those which have originated by the petrifaction or concretion of other matter (obsolete). In later use: fossil organisms.
Origin
Mid 16th century; earliest use found in William Fulke (d. 1589), theologian and college head. From post-classical Latin fossilia rocks or minerals that can be dug out of the earth, use as noun of neuter plural of fossilis obtained by digging.