Kenneth Chapman, in "Graded Readings and Exercises in Old Icelandic" "The noun mathr is the second most frequent noun in Old Icelandic."  But of course he doesn't go on to answer the obvious question.  (I'm sure we all had maddening professors like this--heck some of you may even be one!)  So, what is the most common noun in Old Norse?
 
Thx,
   Alec MacLean