echidna

Coined in scientific literature around 1811. Probably from Ancient Greek ἔχιδνα (ékhidna, “snake, viper”) via Latin echidna. Compare ἐχῖνος (ekhînos, “hedgehog, etc.”). However, this sense is problematic (unless it is a reference to the ant-eating tongue). The name perhaps belongs to Latin echinus (“sea urchin, hedgehog”) from the aforementioned Ancient Greek term's alternate sense of "sea-urchin" (also "sharp points"), which Watkins explains as "snake-eater", from ἔχις (ékhis, “snake”), though it may actually be from Proto-Indo-European *h₁éǵʰis (“hedgehog, hedgehog-like animals”). The 1810 Encyclopaedia Britannica deduces thus the animal's alternative name as "porcupine ant-eater". Alternatively, and perhaps more likely, the name refers to Echidna as the name of a serpent-nymph in Greek mythology, "a beautiful woman in the upper part of her body; but instead of legs and feet, she had from the waist downward, the form of a serpent", in which case the animal was named for its mixed features (early naturalists doubted whether it was a mammal or amphibian). Ultimately, the etymology may be from a synthesis of all the roots above. (From OED.)

1. 01
   derived from *h₁éǵʰis✻
2. 02
   borrowed from echidna
3. 03
   derived from ἔχιδνα