Where does “pliht” come from?

pliht (Old Dutch) comes from Proto-West Germanic plihti, from Proto-West Germanic plehan — to stand up for; to be responsible for.

Ancestry of “pliht”, step by step

Step	Language	Word	Meaning
1	Proto-West Germanic	plihti	care, maintenance, diligence; responsibility,...
2	Proto-West Germanic	plehan	to stand up for; to be responsible for

pliht — Etymology, Origin & Word History | Etymology Explorer