You can refer this blog to understand how to apply CSR.
The code which you can write to modify column names is as below (I am currently modifying "Title"):
(function () {
function preTaskFormRenderer(renderCtx) {
modifyColumns(renderCtx);
}
function modifyColumns(renderCtx)
{
var arrayLength= renderCtx.ListSchema.Field.length;
for (var i=0; i < arrayLength;i++)
{
if(renderCtx.ListSchema.Field[i].DisplayName == 'order_number')
{
var newTitle= "New Title";
var linkTitleField = renderCtx.ListSchema.Field[i];
linkTitleField.DisplayName = newTitle;
}
}
}
function registerRenderer()
{
var ctxForm = {};
ctxForm.Templates = {};
ctxForm.OnPreRender = preTaskFormRenderer;
SPClientTemplates.TemplateManager.RegisterTemplateOverrides(ctxForm);
}
ExecuteOrDelayUntilScriptLoaded(registerRenderer, 'clienttemplates.js');
})();
You can also for loop to find position of a particular field. var linkTitleField = renderCtx.ListSchema.Field[0]; Here "0" refers to the position of the field. As i mentioned above you can iterate over the fields to find the position of the desired column.