Meaning

noun the trait of acting stupidly or rashly

noun a stupid mistake

noun the quality of being rash and foolish

originUncertain. The most common theory is that term primarily denotes a clump of trees and relates to French feuille, feuillée and English foliage; it has also been suggested that it refers to some perceived connection or resemblance of the named place to an architectural folly, but many places so named have no architectural follies and cannot be named directly for them.

Etymology from Wiktionary, CC BY-SA 3.0