I had a similar requirement last week. But unfortunately Tableau does not have anything for this. It just display the field name as you have named it. There is no way you can change it dynamically .
But yes. There is a work around if you are fine using text boxes than displaying field names.
1. Hide the field name
2. Create a text box IN THE DASHBOARD with the dynamic parameter name which u want to give:
This should get what you want. But this not a good practice as the text box may move from its place when the environment changes. But it is a work around.
Hope this helps.