kind of crab
蟳 refers to a specific kind of crab. The meaning is narrow and concrete, without broader abstract extensions.
蟳 is a phono-semantic compound: 虫 (insect/creature) indicates a type of animal, and 尋 likely provides the sound. The exact historical development is uncertain.
The insect radical 虫 suggests a small creature, and the right side 尋 looks like a complex shell or claw pattern. Picture a crab with a patterned shell scuttling sideways.
For ジン, imagine a crab sipping a tiny gin and tonic: gin -> ジン, and the crab's claw holds the glass.