the upper deck in a vessel with only two decks.
the second deck above the inner bottom in a vessel with more than two decks.
Is It Tis Or ‘Tis?According to Google's Ngram Viewer, the contraction 'tis was a fan favorite in the early 1700s. At this time, it was likely used more often than it's.
Origin of tonnage deck
First recorded in 1885–90
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019