A hydra is a many-headed monster of legend, or a tiny freshwater animal. A hydra in the pond.
The monster grew two heads for each one cut off, which is why the word means an unkillable problem. The real animal is a few millimetres long and can regrow from almost any fragment.
1nounhydraA many-headed monster of legend, or a tiny freshwater animal.
“A hydra under the microscope had caught something twice its size.”
hydra is a creature.
From the Hydra of Greek myth, whose heads grew back doubled; the animal is named for its similar regrowth.
Proto-Indo-European
*wed-
English, today
hydra
After the Hydra, from Greek mythology, which grew two new heads every time one of its heads was cut off. The biology sense alludes to the budding method of asexual reproduction that the hydra practices, similar to growing new heads. The figurative sense refers to how the creature could not be killed by a swift, decisive solution (in contrast to a Gordian knot).
Etymology from Wiktionary, CC BY-SA