Emily Dickinson Lexicon

FOL'LY, n. [Fr. folie, from fol, fou; Arm. follez; It. follia. See Fool.]

1. Weakness of intellect; imbecility of mind; want of understanding. A fool layeth open his folly. Prov. xiii.
2. A weak or absurd act not highly criminal; an act which is inconsistent with the dictates of reason, or with the ordinary rules of prudence. In this sense it may be used in the singular, but is generally in the plural. Hence we speak of the follies of youth. Whom folly pleases, or whose follies please. Pope.
3. An absurd act which is highly sinful; any conduct contrary to the laws of God or man; sin; scandalous crimes; that which violates moral precepts and dishonors the offender. Shechem wrought folly in Israel. Achan wrought folly in Israel. Gen. xxxiv. Josh vii.
4. Criminal weakness; depravity of mind. Johnson.