The story
- Proto-Indo-European*h₁néwn̥
- Proto-Indo-European*h₁newn̥(n)ós
- Proto-Italic*nowenos
- Latinnōnus
- Latinnōnārius
- English todaynonary
From the Latin nōnārius, from nōnus (“ninth”) + -ārius (whence the English suffix -ary).
Etymology from Wiktionary, CC BY-SA 4.0.