Where does “ridder” come from?

ridder (Dutch) comes from Middle Dutch riddere, from Middle Dutch rîdere, from Old Dutch rīdere, from Old Dutch rīdan, from Proto-West Germanic rīdan, from Proto-Germanic rīdaną, from Proto-Indo-European rēydʰ-, from Proto-Indo-European h₂er- — to fit, to fix, to put together.

ridder (Dutch): A knight; One of certain butterflies of the...