This file is a resource file for a spell using effect 214 (select spell). When the main spell is cast, this file is used to present several further spell options.
The first column contains identifiers for the spell names.
The second column contains the filename of each spell.
The third column is unknown.
In BG2 ToB we have (spwi417):

2DA V1.0
****
           ResRef     Type       
Mace       SpWi488    3          
Axe        SpWi487    3          
Short_Sword SpWi486    3          
Long_Sword SpWi485    3