a. Of or relating to a lower world of the dead.
b. Of or relating to hell: infernal punishments; infernal powers.
2. Fiendish; diabolical: infernal instruments of war.
3. Abominable; awful: the infernal racket of the jackhammers.
[Middle English, from Old French, from Late Latin īnfernālis, from īnfernus, hell, from Latin, lower, underground; see dher- in the Appendix of Indo-European roots.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.