sternson

stern·son

S0747700 (stûrn′sən)n. Nautical A bar of metal or wood set between the keelson and the sternpost to fortify the joint. Also called stern knee.
[stern + (keel)son.]

sternson

(ˈstɜːnsən) n (Nautical Terms) nautical a timber scarfed into or bolted to the sternpost and keelson at the stern of a wooden vessel. Compare stemson[C19: from stern2 + -son, on the model of keelson]