Related question: “Legend” or “key”?
Legend, also known as a Chart's Key, often located on the right hand side of the chart or graph.
It took me some time to understand what the legend was when learning programming with charting controls. Now I am wondering how this usage originated.
Legend, as used in the film I am Legend is a narrative of human actions How was this word chosen to be used as key in chart?
To a non-technical English speaker, is there difficulty in learning "legend of the chart/legend of the graph", or is this usage intuitive?