The Etymology of Coastal
The connection between a coastline and a rib cage is not obvious until you trace the word back to Latin. Costa meant 'rib' in anatomical Latin, and by extension 'side' or 'flank' — the ribs being the sides of the torso. When Romans described the edge where land met sea, they reached for the same word: the shore was the 'side' of the land, its outermost flank. Old French inherited costa as coste, preserving both the anatomical and geographical senses. Middle English borrowed coste for the shoreline in the 14th century, eventually simplifying it to coast. The adjective coastal arrived late, around 1750, formed by simply adding the suffix -al. Before that, English had used costall, but the newer form won out. The anatomical sense of costa never fully disappeared from English either: intercostal muscles (between the ribs) keep it alive in medical vocabulary. And in one of etymology's odder twists, French côtelette ('little rib') was borrowed into English as cutlet — meaning coastal erosion and a pork cutlet share the same Latin bone.