Where does “どうも” come from?

どうも (Japanese) comes from Japanese も, from Old Japanese も, from Proto-Japonic mə, from Arabic مَن — who?; who.

どうも (Japanese): no matter how, not at all; somehow, something;...

Definitions

どうも traces back through two separate lines of ancestry.

Step	Language	Word	Meaning
1	Japanese	も	Used to form the conjectural form of verbs,...
2	Old Japanese	も	non-unique topic marker: also, even
3	Proto-Japonic	mə	non-unique topic marker: also, even, too, as well
4	Arabic	مَن	who?; who

Step	Language	Word	Meaning
1	Japanese	どう	in what manner, how; what about..; Casual...