Where does “undoynge” come from?

undoynge (Middle English) comes from Old English undōnde, from Proto-Germanic andadōndz, from Proto-Germanic andadōną — to undo.

Ancestry of “undoynge”, step by step

Step	Language	Word	Meaning
1	Old English	undōnde	undoing
2	Proto-Germanic	andadōndz	—
3	Proto-Germanic	andadōną	to undo

undoynge — Etymology, Origin & Word History | Etymology Explorer