device for fastening, c.1300, probably from clamb, perhaps originally past tense of climb, v., or from Middle Dutch clampe (Dutch klamp), from West Germanic *klamp- "clamp, cleat;" cognate with Middle Low German klampe "clasp, hook," Old High German klampfer "clip, clamp;" also probably related to Middle Dutch klamme "a clamp, hook, grapple," Danish klamme "a clamp, cramp," Old English clamm "fetter;" see clam, n..

"to fasten with a clamp," 1670s, from clamp, n.. Related: Clamped; clamping.