jetée

French jetée comes from the past participle of jeter, 'to throw,' from Latin iactare, 'to hurl.' A jetée was originally material thrown into the water to form a barrier or landing — rubble, stone, timber, whatever was at hand. The English spelling jetty appeared by the 1400s, and the word described any structure projecting into a body of water.

Medieval port cities depended on jetties for their economies. The jetty at Acre, built by Crusaders in the 1100s, protected the harbor that supplied the Latin Kingdom of Jerusalem. The mole at Genoa, extended repeatedly between the 1200s and 1500s, was one of the longest jetties in the Mediterranean. These were not casual piers — they were engineering projects that took decades.

English jetties took a different form. Along the coast of Sussex and Kent, wooden groynes — essentially small jetties perpendicular to the shore — were built to prevent beach erosion. The principle was the same as the French jetée: throw material into the water to redirect its force. Brighton's groyne system, established in the 1700s, still shapes the beach today.

The word also moved inland. In architecture, a jetty is an upper floor that projects beyond the floor below — common in medieval timber-framed buildings. The overhang 'juts' or 'jets' outward, and the terminology is identical. Something thrown forward, whether into water or into air.