Dutch word bedanken comes from Middle Dutch danken (To thank [+accusative = for].)

Detailed word origin of bedanken

Dictionary entry	Language	Definition
danken	Middle Dutch (dum)	To thank [+accusative = for].
bedanken	Middle Dutch (dum)	To oblige to thank.
bedanken	Dutch (nld)	(transitive) to thank.

Words with the same origin as bedanken