You may have noticed that when using calculations as headers in Tableau, they are not always appropriately named for the end-user to understand what it actually is. Not only this, but dimensions are unable to be aliased like measures. So, what do you do when you are unable to change the name of a dimension for a header? Thankfully theres a little workaround.
Step 1: Place your dimension on to Rows
Step 2: Double click the dimension in the view
Step 3:
Type // followed by your alias name, like this.
Step 4:
Do shift+Enter Enter and you will see the dimension return to this view
Step 5:
Press enter again and you are finished! Your dimension has been aliased (only in the sheet you did it in)
Advice:
Try not to forget/make a note that you have aliased your dimension this way as it isn't clear it is aliased if someone new is looking at your workbook!