Everybody knows that medical terms, including names for parts of the body, are frequently borrowed from ancient Greek and Latin. Often, the terms derive from what the body part looks like. The tibia, or shin bone, comes from the Latin word for “flute,” for example.
The hippocampus, tucked into the middle of your brain, helps move short-term memories to long-term storage and aids in controlling emotion. In 1587, when Giulio Cesare Aranzi discovered and named this little item, he had no idea of its purpose and so named it based on its shape.
The hippocampus looks like a seahorse. (Here’s a great photograph to illustrate.) Hippo, as you might know, was a Greek horse. (Hippopotamuses are water horses.) The –campus ending meant “sea monster.” The Romans borrowed this word from the Greeks, which gave it the Latinate –us ending and plural (hippocampi).
Maybe you think seahorses are too cute for the “monster” moniker. I’ve always found them to be creepy, as well as cute.
(Thanks, Michael Whitely, for the idea.)