Some genealogists when they have an unknown name want to put something in that blank. That’s why in some databases you will see things such as: Nmi–No Middle Initial Nmn–No Middle Name Lnu–Last Name Unknown Unk–Unknown Blank–Blank [be careful as Blank can be an actual surname] My personal preference is to not use such terms. If you feel the need to put something in the spot, use actual blanks or dashes.  
There’s an update to our GedMatch 2 webinar on our announcement page.
Get the Genealogy Tip of the Day Book
Archives