a longitudinal beam or set of timbers or metal plates fastened inside the hull of a ship along the keel to add structural strength
Origin of keelsonprobably via Dutch kolsem from Danish kjølsvin, altered (infl. by svin, swine) from kjølsvill from kjøl, keel + sville, sill
A timber or girder fastened above and parallel to the keel of a ship or boat for additional strength.
Origin of keelsonAlteration (influenced by keel 1) of Middle English kelswin probably from Old Norse kjölsvīn kjölr keel svīn swine, timber ; see sū- in Indo-European roots.