A modern invented name based on the English word coast, evoking the sea and shoreline.
Coastyn is a modern invented name based on the English word coast, so its imagery is immediate: shoreline, sea air, horizon, and open space. That makes it one of those names whose mood is almost more important than its etymology, because the sound itself carries the setting.
The added -yn ending gives Coastyn a contemporary surname-like polish. It feels inventive, nature-linked, and slightly adventurous, with a built-in sense of movement and distance. As a given name, it belongs to the modern taste for place- and landscape-inspired forms that feel fresh rather than inherited.