Where does “non” come from?

non (Old Spanish) comes from Latin non, from Old Latin noenum, from Proto-Indo-European óynos — one; single.

Ancestry of “non”, step by step

StepLanguageWordMeaning
1Latinnonnot
2Old Latinnoenum—
3Proto-Indo-Europeanóynosone; single
Every word from Proto-Indo-European óynos →Every word from Old Latin noenum →Every word from Latin non →