Laying Out and Formatting a Chart : Formatting axis titles, markers, lines, and labels : Working with an axis title : How to format an axis title
 
How to format an axis title
In Axis Title, shown in Figure 17‑77, you can position the title above or below an x-axis, or you can position the title to the left or right of a y-axis. You can outline the title, and add padding around it using Insets. You can change the size and style of the font, and add a shadow or a background color.
Figure 17‑77 Formatting options for an x-axis title