noun, masculine/bu.kli.je/plural: boucliers
shield (broad piece of defensive armor, held in hand, formerly in general use in war, for the protection of the body); shield (anything which protects or defends)
“levée de boucliers” — outcry, protest
Ellipsis of Old French escut boucler (“shield with a buckle”), with change of suffix. Morphologically, from boucle + -ier.