Where does “թթու” come from?

թթու (Armenian) comes from Old Armenian թթու, from Old Armenian թութ-.

թթու (Armenian): sour; bitter, harsh, grievous; marinated food;...

Definitions

Step	Language	Word	Meaning
1	Old Armenian	թթու	acid, sour, tart, sharp; bitter, harsh, grievous,...
2	Old Armenian	թութ-	—

թթու — Etymology, Origin & Word History | Etymology Explorer