Geochart: Tooltip without region name

[Pirate X]

Code -

 function drawRegionsMap() {

    var data = new google.visualization.DataTable();

    data.addColumn('string', 'Województwo');

    data.addColumn('number', 'Frekwencja');

    data.addColumn({type: 'string', role: 'tooltip', p:{html:true}}, 'ToolTip');

    data.addRows( [

                  ['PL-DS', 60, '<p>Dolnośląskie</p>60%'],

                  ['PL-KP', 62, '<p>Kujawsko-Pomorskie</p>62%'], 

                  ['PL-LU', 59, '<p>Lubelskie</p>59%'], 

                  ['PL-LB', 61, '<p>Lubuskie</p>61%']

                  ])

    var options = {

        region: 'PL',

        resolution: 'provinces',

        datalessRegionColor: 'transparent',

        displayMode: 'regions',

        tooltip: {

            isHtml: true

        }

    };

    var chart = new google.visualization.GeoChart(document.getElementById('regions_div'));

    chart.draw(data, options);

}

Output

Question -

How to remove the Region Name ?

If it is not recommended to remove the name, any documentation which says it's not possible/suggests workarounds ?

What's the best practice in this scenario ?