Where does “Trōiān” come from?

Trōiān (Old English) comes from Latin Trōiānus, from Latin Trōia, from Ancient Greek Τροία — Troy.

Ancestry of “Trōiān”, step by step

Step	Language	Word	Meaning
1	Latin	Trōiānus	—
2	Latin	Trōia	—
3	Ancient Greek	Τροία	Troy