Can you give us the context in which this word is used? 

It shows up during "Fix Errors".   Below is what the page displays:

Check This Entry

Schedule IL-WIT Income Tax Withheld: Spein must be entered.

Spein:   <enter value>

All, this refers to the "Federal ID" of the payer on your W-2.  If you received unemployment benefits it will be the "IDES Federal ID" on your 1099-G form.

Could that be the "SPouse's"  EIN on their W-2 form in the state section box 15 ?