Many etymologies of animals' names are pretty straightforward. Fish, for instance, comes from a source that meant fish. The original word for fly meant to fly. Ho hum. Some names for critters, though, are a tad more interesting.
Plover made its way to English around 1300 from Vulgar Latin through French. Its original meaning was belonging to rain. Apparently the plover made its migratory way through the British Isles just as the rainy season began.
Frog comes from fruska, a Proto-Germanic word meaning hop, and has been with us since we started calling the language English.
Another word that came to English as Old English was born is weasel. It came from the Proto-Germanic word, wisulon, & means stinking animal. Interestingly, wisulon is also the grandmother word to another slightly larger animal with a distinctive smell, the bison.
In the mid-1400s, caterpillar came to English from the French word chatepelose, meaning shaggy cat. Apparently, many languages named the caterpillar after other animals: American English - wooly bear, Portuguese – lizard, Italian – both little cat & little dog.
Narwhal came to English in the 1650s through Danish & Norwegian from the Old Norse word nahvalr. The pale hide of this animal inspired the Old Norse to call it the corpse-whale (na- meaning corpse & hvalr meaning whale).
Muskrat made it into English in the 1610s from the Algonquian word muscascus, which meant it is red.
The very unlikely animal the platypus got its name, not from any number of unexplainable physical characteristics, but from its flat feet. Platy is Greek for flat & pus is Greek for foot. Platypus came to English in 1799.
Shark arrived in English in the 1560s. Its origin is a complete mystery.
Good readers, I’m hoping you’ll suggest a critter or two in the comments section. I’m hoping to do a second critter etymology post.