Gibraltar rock

from The Collaborative International Dictionary of English v.0.48

Gibraltar \Gi*bral"tar\, n.
   1. A strongly fortified town on the south coast of Spain,
      held by the British since 1704; hence, an impregnable
      stronghold.
      [Webster 1913 Suppl.]

   2. A kind of candy sweetmeat, or a piece of it; -- called, in
      full, {Gibraltar rock}.
      [Webster 1913 Suppl.]