Nowadays, people think of parasites as tapeworms, ticks, or the like, but this entomological usage was etymologically used differently before science showed up in the seventeenth century. Before being appropriated for those disgusting organisms, parasite literally meant "a PERSON who lives off of others", showing that this newer definition is in fact a metaphor. Since the Romans, too, had a plethora of needy clingy people (I believe they were called plebeians), it is not surprising that our word is from Latin parasitus. And since the Greeks were even worse, how weird is it really that it all comes from parasitos? Since parasitical people worm their way into dining opportunities, parasitos literally meant "to eat at the table of another". This is from para- ("beside") and sitos ("food"). We have no clue where sitos derives from, but para- is a common prefix even in English, and comes from Proto-Indo-European per, or "forward". This whole origin story is ironic because, far from being beside food, modern parasites are surrounded by it!
Adam Aleksic, a rising sophomore studying linguistics and government at Harvard University, has been described as the internet's sixth most famous etymologist. He also has disturbing interests in politics, vexillology, geography, board games, conlanging, and law.