One option would be to select the first two words, then run a macro that uses the Selection property to get those selected words in a string variable, add any other chars you want to the string, then SaveAs.

Sub SaveAsFirstTwoWords()
Dim NameString As String
Dim PathString As String
   If Selection.Type = wdSelectionNormal Then
       PathString = "C:\wherever\wherever\wherever"
       NameString = PathString & Selection & "WhateverElse"
       ActiveDocument.SaveAs FileName:=NameString
   Else
       MsgBox "Nothing is Selected"
       End
   End If
End Sub

You could put that macro in a drop-down menu, a toolbar button, or a hotkey. Select the first two words of the file, then run it.

Oh, and to avoid overwriting existing files, you might want to add something
like this:

Dim fs
Set fs = CreateObject("Scripting.FileSystemObject")

If fs.FileExists(NameString) Then
           ActiveDocument.SaveAs FileName:=NameString
       Else
           MsgBox "Honk off, Bozo. " & NameString & " already exists."
           End
       End If

Well, that'll larn me to post when I'm groggy with fattygue.

I gooned up the check for the file. Try it this way:

Sub SaveAsFirstTwoWords()
Dim NameString As String
Dim PathString As String
Dim fs

Set fs = CreateObject("Scripting.FileSystemObject")

   If Selection.Type = wdSelectionNormal Then
       PathString = "C:\" 'wherever\wherever\wherever"
       NameString = PathString & Selection & ".doc"
       If Not fs.FileExists(NameString) Then
           ActiveDocument.SaveAs FileName:=NameString
       Else
           MsgBox "Honk off, Bozo. " & NameString & " already exists."
           End
       End If
   Else
       MsgBox "Nothing is Selected"
       End
   End If
End Sub