(buk′əl) noun
1. A metal frame with movable tongue for fastening together two loose ends, as of straps, etc.
2. An ornament for shoes, etc., devised like a buckle.
—v.t.
1. To fasten or attach with or as with a buckle.
2. To apply (oneself) assiduously.
—v.i.
3. To apply oneself vigorously: often with down to or to.
4. To fight; grapple. [<F boucle cheek-strap, boss of a shield <L buccula, dim. of bucca cheek]

(buk′əl) v.t. & v.i. ·led, ·ling
To bend under pressure; warp, curl, or crumple.
—noun A bend; in mechanics, a permanent distortion or bend. [<F boucler bulge]

(buk′əl), Henry Thomas,
1821–62, English historian.