Where does “freely” come from?

Freely comes from Middle English frely, from Old English frēolīc, meaning not in bondage or at liberty.

freely (English): Free; frank; Generous; noble; excellent;...

Definitions

Step	Language	Word	Meaning
1	Middle English	frely	—
2	Old English	frēolīc	free, freeborn, glorious, stately, magnificent,...

freely — Etymology, Origin & Word History | Etymology Explorer