Thank you!
Might be this function: (SoundSource / src / SSAudioDeviceCenter.m : 65)

- (NSString*)name
{
	OSStatus err;
	UInt32 size;
	NSString* deviceName = nil;
	NSString* sourceName = nil;
	{
		size = sizeof(deviceName);
		err = AudioDeviceGetProperty( [self coreAudioDeviceID], 0, [self coreAudioIsInput], kAudioDevicePropertyDeviceNameCFString, &size, &deviceName);
		if( err  )
			deviceName = nil;
	}
	if( _sourceType != 0 )
	{
		AudioValueTranslation trans;
		trans.mInputData		= &_sourceType;
		trans.mInputDataSize	= sizeof(_sourceType);
		trans.mOutputData		= &sourceName;
		trans.mOutputDataSize	= sizeof(sourceName);
		size = sizeof(AudioValueTranslation);
		err = AudioDeviceGetProperty( [self coreAudioDeviceID] , 0, [self coreAudioIsInput], kAudioDevicePropertyDataSourceNameForIDCFString, &size, &trans);
		if( err )
			sourceName = nil;
	}
    // If AirPlay or >1 source on device, use DeviceName: SourceName (doesn't match Sound prefpane, but is much easier to understand)
	if( ( sourceName && ![sourceName isEqual: deviceName] ) &&
        (
          ( !AudioDeviceGetPropertyInfo([self coreAudioDeviceID], 0, [self coreAudioIsInput], kAudioDevicePropertyDataSources, &size, NULL) && ( size > sizeof(UInt32) )
          ) || ( [self coreAudioTransportType] == kAudioDeviceTransportTypeAirPlay )
        )
      )
    {
        return [NSString stringWithFormat: @"%@: %@", deviceName, sourceName];
	}
	return sourceName ? sourceName : deviceName;
}

Maybe you'll find a hint digging thro this: https://github.com/nriley/SoundSource or this ./SoundSource-250.zip since they were able to show the individual devices since 10.5. Unfortunately it's broken since 10.9 :-/