StrSetNthEffectItemScriptName

Function:

StrSetNthEffectItemScriptName spell:ref index:long newName:stringID 

Example:

long newName

set newName to StrNew "Dark Shroud"
Player.StrSetNthEISName DANamiraDarkness 0 newName

If the magic item in spell at position index (starting from 0) is scripted, sets its name to newName.