Where does “-ung” come from?

-ung (Middle High German) comes from Old High German -unga, from Proto-Germanic -ungō — -ing, -ion. "Forms gerund nouns from verbs.".

Ancestry of “-ung”, step by step

Step	Language	Word	Meaning
1	Old High German	-unga	-ing
2	Proto-Germanic	-ungō	-ing, -ion. "Forms gerund nouns from verbs."

-ung — Etymology, Origin & Word History | Etymology Explorer