1749, "two-edged, heavy broadsword of ancient Scottish Highlanders," from Gaelic claidheamh mor "great sword," from claidheb "sword" (compare Welsh cleddyf), which is possibly from a PIE root *kel- "to strike" (see holt) + mor "great" (compare Welsh mawr; see more).
An antiquarian word made familiar again by Scott's novels. It was sometimes applied inaccurately to 16c.-18c. one-handed basket-hilted broad swords. Modern military application to a type of pellet-scattering anti-personnel mine is first attested 1962.