Label

Command: label <item> as <label> | remove <item>
The item must be in your inventory and can only be labeled once.
Example: 'label key as tower key' will allow you to target 'tower key' and will show up in inventory as 'key labeled tower key'. Chests can be labelled permanently with this. Note that a chest must be on the ground in a castle room for this to work.
Labels can be removed with 'label remove <item>'.
Multiple item option:
label all <blah> as <blah2>
These items must be in your inventory.