Darwin and Derwin could be considered as modern English forms of the Old English feminine name "Deorwynn" [in the Submitted Names Database] meaning "Beloved (or dearest) joy" (Source: https://anglisc.miraheze.org/wiki/Anglish_Given_Names).Darwin could be Latinized to become "Darwina" or "Darwinna". Based on endings of other Old English feminine names ending in -wynn (like -wyn, -wynne, -wyna, -wen, -wena and -wenna), I imagine that Darwynn, Darwyn, Darwynne, Darwyna, Darwen, Darwena and Darwenna could work as other forms.Derwin could be Latinized to become "Derwina" or "Derwinna". Based on endings of other Old English feminine names ending in -wynn (like -wyn, -wynne, -wyna, -wen, -wena and -wenna), I imagine that Derwynn, Derwyn, Derwynne, Derwyna, Derwen, Derwena and Derwenna could work as other forms.Unfortunately I can't find sources showing these though.
Darwin could be Latinized to become "Darwina" or "Darwinna". Based on endings of other Old English feminine names ending in -wynn (like -wyn, -wynne, -wyna, -wen, -wena and -wenna), I imagine that Darwynn, Darwyn, Darwynne, Darwyna, Darwen, Darwena and Darwenna could work as other forms.
Derwin could be Latinized to become "Derwina" or "Derwinna". Based on endings of other Old English feminine names ending in -wynn (like -wyn, -wynne, -wyna, -wen, -wena and -wenna), I imagine that Derwynn, Derwyn, Derwynne, Derwyna, Derwen, Derwena and Derwenna could work as other forms.
Unfortunately I can't find sources showing these though.