Use the Rename command to change the names associated with Blocks, Layers, LineStyles, RichLineStyles, TextStyles, TableStyles, DimensionStyles, Custom Coordinate Systems, and views.
For certain drawing entities, standard items cannot be renamed or deleted because the drawing for these types must contain at least one basic item, including the:
To rename styles and drawing elements:
You can specify the item to rename directly, by matching name. With the category selected in the list, type or paste the name of the item to rename in the Old name field. The specified item is highlighted in the list.
Access
Command: Rename
Menu: Format > Rename
Ribbon: Manage > Drawing > (Flyout) Rename