AssetDatabase.RenameAsset
static function RenameAsset(pathName: string, newName: string): string;
static string RenameAsset(string pathName, string newName);
static def RenameAsset(pathName as string, newName as string) as string
Parameters

pathName The path where the asset currently resides.
newName The new name which should be given to the asset.
Returns
string An empty string, if the asset has been successfully renamed, and an error string otherwise. All paths are relative to the project folder. Like: "AssetsMyTextureshello.png".
Description

Rename an asset file.