Where does “eintrocknen” come from?

eintrocknen (German) comes from German trocknen, from German trocken, from German -en, from Middle High German -en, from Old High German -īn, from Proto-Germanic -īnaz, from Proto-Indo-European -iHnos, from Proto-Indo-European -no- — adjectival suffix.

eintrocknen (German): to dry out, to dry up with a focus on leaving behind a dried remainder, e.g. of blood, ink, paint, etc