in·fi·del (ĭnfĭ-dəl, -dĕl′)
1. Often Offensive An unbeliever with respect to a particular religion, especially Christianity or Islam.
2. One who has no religious beliefs.
3. One who doubts or rejects a particular doctrine, system, or principle.
[Middle English infidele, from Old French, from Latin īnfidēlis, disloyal : in-, not; see IN-1 + fidēlis, faithful (from fidēs, faith; see bheidh- in the Appendix of Indo-European roots).]
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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.