the mind > mental capacity > lack of understanding > foolishness, folly > besottedness, infatuation > [adverb]
1876 J. Weiss v. 154 The fair maid [Ophelia] who must be the tenant of this grave so fatuously dug.
1882 M. E. Braddon I. i. 18 Such wild youths, she told herself, fatuously, generally make the best men.