Changing field names
When you change a field name, FileMaker Pro changes the name on each layout and any field references used in calculation or summary fields. The field label changes on layouts if it matches the original field name.
To change a field name:
1.
With the database open, choose File menu > Manage > Database.
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For Field Name, type or paste the new name.
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Click Change.
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To change a field name in Table View:
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Related topics 
About naming fields
Using a reserved word or symbol for a field or table name