Topic summary
Quai
Extracted from the Wikipedia article Wharf.
Quay
Quay, on the other hand, has its origin in the Proto-Celtic language. Before it changed to its current form under influence of the modern Frenchquai, its Middle English spelling was key, keye or caye. This in turn also came from the Old Normancai (Old French / French chai "wine cellar"), meaning originally "earth bank near a river", then "bank built at a port to allow ship docking". The French term quai comes, through Picard or Norman-French, from Gaulishcaio, ultimately tracing back to the Proto-Celtic *kagio- "to encompass, enclose". Modern cognates include Welshcae "fence, hedge" and Cornishke "hedge".