unaccountably

from WordNet (r) 3.0 (2006)

unaccountably
    adv 1: in an unaccountable manner; "in the book, a tycoon
           unaccountably becomes the hero's friend"

from The Collaborative International Dictionary of English v.0.48

Unaccountable \Un`ac*count"a*ble\, a.
   1. Not accountable or responsible; free from control.
      --South.
      [1913 Webster]

   2. Not to be accounted for; inexplicable; not consonant with
      reason or rule; strange; mysterious.
      [1913 Webster] -- {Un`ac*count"a*ble*ness}], n. --
      {Un`ac*count"a*bly}, adv.
      [1913 Webster]
      [1913 Webster]