There's no native way to do this in Tableau that I can think of. However, you could look to edit the XML and rename the columns that way but I personally wouldn't recommend this approach.
It sounds like you're connecting to a database table - are you able to use custom SQL instead? If so, you could create custom SQL to do the aliasing of the columns.
[Asset Id] as [Asset_Number],
[Column2] as [Wombats],
Thank you Tom, I can use a custom SQL. I really didn't want to use the aliasing because of the volume of columns and with the scope of changing the alternate labels again in future, I was checking if there is a solution that is useful for folks who don't know sql querying as well..