Have you every wondered where the German word for Christmas, Weihnachten, comes from? I have, as it is so different from words for Christmas in other European languages. So I decided to investigate.

Weihnachten comes from the Middle High German wīhenahten ‎(Christmas), from a dative plural ze den wīhen nahten ‎(in the holy nights). The oldest form (1170) is a singular diu wīhe naht (the Holy Night). It came to refer to Christmas Eve and Christmas Day collectively somewhat later.

Source: Wiktionary

Another source states that Weihnachten first appeared as ze wîhen naht in a song by the minstrel Spervogel, who lived in the 12th Century: “Er ist gewaltic unde starc (…) der ze wîhen naht gebórn wárt. (…) daz ist der heilige Krist, (…) jâ lobt in allez, daz dir ist”. It is perhaps a translation of the Latin nox sancta.

More about German Christmas vocabulary and traditions:
http://marathonsprachen.com/christmas-vocabulary-wortschatz-zur-weihnachten/