langue d'o·ïl (doil, doi, dô-ēl)
The Romance language of medieval France north of the Loire River, on which modern French is based.
[French, from Old French : langue, language; see LANGUAGE + de, of; see LANGUE D'OC + oil, yes (ultimately from Latin hoc ille (fēcit), he (did) this : hoc, this; see OCCITAN + ille, he; see al-1 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.