Where does “ともなく” come from?

ともなく (Japanese) comes from Japanese も, from Old Japanese も, from Proto-Japonic mə, from Arabic مَن — who?; who.

Ancestry of “ともなく”, step by step

ともなく traces back through 3 separate lines of ancestry.

via Japanese

StepLanguageWordMeaning
1JapaneseUsed to form the conjectural form of verbs,...
2Old Japanesenon-unique topic marker: also, even
3Proto-Japonicnon-unique topic marker: also, even, too, as well
4Arabicمَنwho?; who

via Japanese

StepLanguageWordMeaning
1Japanesewith; and; a particle following a phrase or...
2Old Japanese
3Proto-Japonicplace
4Proto-Uralicthat

via Japanese ない

StepLanguageWordMeaning
1Japaneseないhaving that quality, having that state; very much...
2Old Japaneseない
Every word from Arabic مَنEvery word from Proto-Japonic Every word from Old Japanese