From Latin 'costa' (rib, side) — the coast is the 'rib' of the land, its flank facing the sea.
The part of the land near the sea; the edge of the land facing the ocean.
From Old French coste (rib, side, hillside, shore, coast), from Latin costa (rib, side of the body, side of a building, flank). Latin costa is of uncertain deeper etymology but may derive from PIE *kost- (bone, rib), related to Old Slavic kosti (bone) and possibly to PIE *kes- (to cut, to divide). The metaphor underlying the word is the rib or side of the land — the coast is where land ends
A 'coast' is a 'rib.' Latin 'costa' meant 'rib' and then 'side,' and the coast is the side of the land where it meets the sea. 'Accost' (to approach boldly) originally meant 'to come alongside' — to draw up rib-to-rib. And a 'cutlet' is a 'little rib' (French 'côtelette,' diminutive of 'côte,' rib).