Late 17th century; earliest use found in John Webster (1611–1682), schoolmaster and polemicist. From classical Latin terrificusterrific + -al Compare earlier terrific.
Definition of terrifical in US English:
terrifical
adjectivetəˈrɪfɪkl
rare
Relating to terror; terrifying; terrific.
Origin
Late 17th century; earliest use found in John Webster (1611–1682), schoolmaster and polemicist. From classical Latin terrificus terrific + -al Compare earlier terrific.