Where does “goodwin” come from?

Goodwin comes from Old English gōd, from Proto-Germanic gōdaz, ultimately from Proto-Indo-European gʰedʰ-, a root of uncertain meaning.

Ancestry of “goodwin”, step by step

Step	Language	Word	Meaning
1	Old English	gōd	a good thing, advantage, benefit, gift; good,...
2	Proto-West Germanic	gōd	good
3	Proto-Germanic	gudą	invoked one; god, deity
4	Proto-Germanic	gastiz	stranger, guest
5	Proto-Indo-European	gʰóstis	stranger, host
6	Proto-Indo-European	-tis	Derives abstract/action nouns from verb roots