keelson is a nautical term for "a timber or girder fastened above and parallel to the keel of a ship or boat for additional strength." According to the Oxford Dictionary of English Etymology, it's an alteration of Middle English kelswayn, probably from Low German kielswīn (whence also German kielschwin, Danish kølsvin, Swedish kölsvin), a combination of kiel "keel" and swīn "swine". It seems that terms for animals, like cat, dog, horse, and swine were used to refer to timber.
swine and its various Germanic cognates are from the Proto-Indo-European root *suh₁- "pig" (in the suffixed form *suh₁-īno-, this seems to be the -no- adjectival suffix that survives in English past participle -en). *suh₁- became Greek ὗς hūs "swine", then ὕαινα huaina "hyena", then Latin hyaena, borrowed thru Old French and into English as hyena, an animal with piglike characteristics.
According to the AHD, the suffixed form *su-kā- became Proto-Celtic *hukk-, then Old English hogg, then Modern English hog. Chambers seems to agree but the ODEE doesn't.
Also according to the AHD *suh₁- is a contraction of seuh₁- "to give birth". This is the source of English son.