A wildcatter is an American term for a person who drills wildcat wells, which are oil wells drilled in areas not known to be oil fields. A wildcatter notable for his success was Texan oil tycoon Glenn McCarthy.
The term dates from the early oil industry in western Pennsylvania. For instance, the Titusville Herald noted in 1880:
One explanation of the term is that it derived from wildcat banking and came to be applied to risky oil ventures. Another explanation is that wildcat wells were drilled far from existing settlements, where only wildcats lived. But wildcat was American slang for any risky business venture by 1838, long before the petroleum industry.[2]