A devilish and cunning plan to take over the world is an example of a diabolical plan.
Origin of diabolical
- From Middle English deabolik from Old French diabolique from Late Latin diabolicus from Latin diabolus devil devil
From American Heritage Dictionary of the English Language, 5th Edition
- First attested between 1350 and 1400 from Middle English diabolik, from Middle French diabolique, from Late Latin diabolicus, from Ancient Greek Î´Î¹Î±Î²Î¿Î»-Î¹ÎºÏŒÏ‚ (diabolikos, “devilish"), from Î´Î¹Î¬Î²Î¿Î»Î¿Ï‚ (diabolos).