13th cent. From Latin december "December" (lit. "the tenth month"). December was the tenth month in the ancient Romulan calendar, but was moved to the twelfth position after Rome adopted the Republican calendar. From decem "ten" and mens "month." See diez and mes respectively.
Portuguese dezembro, Galician decembro, Catalan desembre, French décembre, Italian dicembre, Aromanian dechemvriu, Romanian decembrie