If you drag it off the pivot and back on the list, the name reverts back to the column heading. When you drag it back onto the list it is given the prefix of the operation. Like (Count, Sum, Min, Max...)
So two things are working here: Name of column head and operation.
I believe you would have to do VBA to change it.
I just recorded a macro to change the heading of one of my pivots from "Min of Ch Tank In" to "Min In" and got the following VBA code. Perhaps you can write a little routine to do what you need.
So the thing we are changing in called the DataPivotField.PivotItems(.....).Caption.
hope this gets you closer to your need.
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