"spiked metal ring for holding a belt, etc.," c. 1300, bukel, from Old French bocle "boss (of a shield)," then "shield," then by further extension "buckle, metal ring," (12c., Modern French boucle), from Latin buccula "cheek strap of a helmet," in Late Latin "boss of a shield," diminutive of bucca "cheek" (see bouche).

Boucle in the middle ages had the double sense of a "shield's boss" and "a ring"; the last sense has alone survived, and it metaph. developed in the boucle de cheveux, ringlets. [Kitchin]

"distort, warp, bend out of shape" 1520s, bokelen "to arch the body," from French boucler "to bulge," from Old French bocler "to bulge," from bocle "boss of a shield" (see buckle (n.)). Meaning "to bend under strong pressure" is from 1590s (figurative from 1640s) . Related: Buckled; buckling.

1670s, "clasp, buckle, brooch," from Latin fibula "clasp, brooch; bolt, peg, pin," related to figere "to drive in, insert, fasten" (from PIE root *dheigw- "to stick, fix"). In reference to brooches, the modern English word mostly is used in archaeology. As "smaller bone in the lower leg" from 1706, from a Latin loan-translation of Greek perone "small bone in the lower leg," originally "clasp, brooch; anything pointed for piercing or pinning;" the bone was so called because it resembles a clasp such as that found in a modern safety pin. Related: Fibular.

"to clasp, confine with a buckle, ring, clasp, or the like," especially of the sexual organs, to prevent copulation, 1620s, from Latin infibulatus, past participle of infibulare "to close with a clasp," from in- "on" (from PIE root *en "in") + fibula "a clasp, pin" (from PIE root *dheigw- "to stick, fix"). Related: Infibulated.

This operation was very generally practised in antiquity upon both young men and young women, but in later times chiefly upon the latter; and it is said to be still in use in some parts of the East. [Century Dictionary, 1902]