Where does “Giresun” come from?

Giresun (English) comes from Turkish Giresun, from Ancient Greek Κερασοῦς, from Ancient Greek -οῦς — -ful.

Ancestry of “Giresun”, step by step

Step	Language	Word	Meaning
1	Turkish	Giresun	—
2	Ancient Greek	Κερασοῦς	—
3	Ancient Greek	-οῦς	-ful