Adding title to the legend items is not possible as of now. However, you can use subtitles to make it look like title for the legend items by placing the legend at the top of the chart, as shown in the below code snippet.
subtitles: [{
text: "Language Shares"
}],
legend: {
verticalAlign: "top"
},
Check out this JSFiddle for complete code.
—-
Manoj Mohan
Team CanvasJS