Where does “kreftic” come from?

kreftic (Middle High German) comes from Old High German kreftīg, from Proto-Germanic *kraftīg, from Proto-Germanic kraftugaz — powerful, mighty.

Ancestry of “kreftic”, step by step

Step	Language	Word	Meaning
1	Old High German	kreftīg	—
2	Proto-Germanic	*kraftīg	—
3	Proto-Germanic	kraftugaz	powerful, mighty

kreftic — Etymology, Origin & Word History | Etymology Explorer