sting-ray (n.)

Old English stingan "to stab, pierce, or prick with a point" (of weapons, insects, plants, etc.), from Proto-Germanic *stingan (source also of Old Norse stinga, Old High German stungen "to prick," Gothic us-stagg "to prick out," Old High German stanga, German stange "pole, perch," German stengel "stalk, stem"), perhaps from PIE *stengh-, nasalized form of root *stegh- "to stick, prick, sting."

Specialized to insects late 15c. Intransitive sense "be sharply painful" is from 1848. Slang meaning "to cheat, swindle" is from 1812. Old English past tense stang, past participle stungen; the past tense later leveled to stung.

"a skate, type of fish related to sharks and noted for its broad, flat body," early 14c., raie, from Old French raie (13c.) and directly from Latin raia. De Vaan describes this as a word of unknown origin but with apparent cognates in Germanic (Middle Dutch rogghe, Old English reohhe), perhaps a loan-word from a substrate language. The old etymology (Century Dictionary, etc.) was that the fish was so called from its resemblance to the rays of a fan and from the source of ray (n.1).

All skates are rays, but all rays are not called skates, this name being applied chiefly to certain small rays of the restricted genus Raia, of both Europe and America. [Century Dictionary]