SG Heritage Dictionary

Coamings [Noun] Webster's Dictionary 1828

In ships, the raised borders or edges of the hatches, made to prevent water from running into the lower apartments from the deck.

Coamings [Noun plural] Webster's Dictionary 1913

Raised pieces of wood of iron around a hatchway, skylight, or other opening in the deck, to prevent water from running bellow; esp. the fore-and-aft pieces of a hatchway frame as distinguished from the transverse head ledges.