function MakeTempFilename(
    const APath: String = ''
): string;

String - The unique temporary file name.

MakeTempFilename is a String function used to construct a unique file name for a temporary file. MakeTempFilename encapsulates the platform-specific procedures and functions used to construct a unique file name for an Operating System file. 

APath is a path specifier for the unique file name. 

For the Windows platform, the WIN32 API function used is GetTempFileName, and the tempory file name includes the value in APath and the suffix 'Indy'. 

On the Linux platform, tempnam is called to create the temporary file name. APath in not used or include in the tempory file name on the Linux platform.