the mind > mental capacity > lack of understanding > foolishness, folly > giddiness, empty-headedness > [noun] > instance of
1875 16 Oct. 2/4 Dat's some more ob dat tom-foolishness.
1889 J. K. Jerome v. 65 Of all the silly, irritating tomfoolishness by which we are plagued, this ‘weather-forecast’ fraud is about the most aggravating.
2011 (Nexis) 26 Sept. Parents back in my day laid down the law about tomfoolishness.