Google Analytics columns can be renamed in the Data Pipeline, using a Rename Columns step.
1. Add a Rename Column step in the Data Pipeline.
2. Select the column you would like to rename in the dropdown, and enter the new name in the text input box.
In this example, we're renaming "ga:pageviews" to Pageviews.
Note: if you are using the column name in any Formulas in the Data Pipeline, make sure you're using the new column name if the Formula occurs after the rename.