means a star-shaped marine animal (an echinoderm, not actually a fish) with five or more radiating arms that creeps along the seabed and eats by everting its stomach onto its prey.

from A plain English compound of "star" + "fish," naming the obvious: a sea creature shaped like a star. "Star" descends from Old English steorra, a word with deep Germanic roots and Latin/Greek cousins (stella, aster). "Fish" is the old catch-all for almost anything that lived in water — which is why early namers, untroubled by zoology, lumped this spiny radial animal in with the fishes. Biologists now wince and call it a sea star, since it has no backbone, no gills, and no business being called a fish.