n.
a flat rectangular or oval frame with a hinged pin, used for joining the ends of a belt or strap.
v.
- fasten or decorate with a buckle.
- bend and give way under pressure.
-
(buckle down)
tackle a task with determination.
Etymology
ME: from OFr. bocle, from L. buccula ‘cheek strap of a helmet’, from bucca ‘cheek’; sense 2 is from Fr. boucler ‘to bulge’.