An Etymological Dictionary of the German Language/Annotated/neun
neun, numeral, ‘nine,’ from the equivalent Middle High German and Old High German niun; corresponding to Gothic niun, ‘nine,’ Old Saxon nigun, Dutch negen, Anglo-Saxon nigun, English nine, Old Icelandic níu (all these represent *nī̆jun?); a common Aryan numeral, like all the units. Compare Sanscrit návan, Latin novem, Greek ἐννέα, Old Irish nói. It has been supposed that the common Aryan word for neun (newn) is derived from neu (néwos), ‘nine’ being regarded as the ‘new number’ of the third tetrad; the system of reckoning by fours must be assumed as the oldest in the Aryan languages, since the numeral acht, ‘eight,’ is a dual form.