Where does “terganą” come from?

terganą (Proto-Germanic) comes from Proto-Indo-European derHgʰ- — to tug, to stretch; to pluck.

Ancestry of “terganą”, step by step

Step	Language	Word	Meaning
1	Proto-Indo-European	derHgʰ-	to tug, to stretch; to pluck

terganą — Etymology, Origin & Word History | Etymology Explorer