A type of diving bird, particularly the grebe, known for diving deep into water; also a daring aviator or stunt flier.
Compound of 'hell' and 'diver.' The bird name emerged in American English (1800s) because these grebes dive so suddenly and completely they seem to vanish. Aviation usage followed for reckless pilots.
Grebes are so committed to diving that they position their legs at the extreme rear of their bodies—they literally sacrificed running ability for diving expertise, which is why people were amazed enough to give them this intense name!
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