An index can be renamed with the sp_rename statement. An index can be renamed only if the index name is unique within the table.
sp_rename 'Students.Index_Name_Clstd_FF10', 'ClstdIndex_Name_FF10';
Caution: Changing any part of an object name could break scripts and stored procedures.
The index was renamed to 'ClstdIndex_Name_FF10'.In the above example the name of the index, Index_Name_Clstd_FF10, is renamed to ClstdIndex_Name_FF10.