I don't know the full story on this, but the list of names you can select
from consists of at least the following:
a. names of the worksheets in your Workbook, followed by "$" , which I
believe is just another way of representing the "!" that you see in range
names in Excel.
b. range names, which can be created in a number of ways, e.g.
 - if you use Data|List|Create List to create a list in Sheet 1, you will
probably end up with a range name like

Sheet1!_FilterDatabase

This may actually show up as "Sheet1$_" in the list that Word displays

 - if you use one of the options in Data|Import|External Data to import or
connect to external data, Excel creates a range name associated with the
sheet where you place the data, e.g. Sheet1!default__VA_EXPCUSTOMER, which
will show up in Word as Sheet1$default__VA_EXPCUSTOMER.

 - if you use Insert|Name|Define, Excel creates a range name associated
with the Workbook as a whole, e.g. "myname". These show up in Word's list as
is, e.g. "myname".

Peter Jamieson