keelson
Concise Oxford English Dictionary © 2008 Oxford University Press:
keelson /ˈkiːls(ə)n/ (also kelson)
▶noun a structure running the length of a ship, that fastens the timbers or plates of the floor to the keel.
– origin ME kelswayn, related to Low Ger. kielswīn, from kiel ‘keel of a ship’ + swīn ‘swine’ (used as the name of a timber).
'keelson' also found in these Oxford entries:

