Mid 18th century; earliest use found in Patrick Murdoch (d. 1774), Church of England clergyman and writer. From petroleum + -ous, after German steinölig.
Definition of petroleous in US English:
petroleous
adjectivepɪˈtrəʊlɪəs
Containing petroleum; rich in petroleum.
Origin
Mid 18th century; earliest use found in Patrick Murdoch (d. 1774), Church of England clergyman and writer. From petroleum + -ous, after German steinölig.