A parasite is often ingested alongside food, so is it really that surprising that the word itself means "beside food"? Because that's exactly the case. However, it's not for the reason I just listed. Originally, parasite only referred to humans who mooched off other humans, and got applied to other animals in the mere 1600s. So, through French parasite and Latin parasitus, the word traces back to the Ancient Greek word, which still meant the same thing, but literally could be defined as "one who eats at another's table". This is a portmanteau of the word para, meaning "beside" (from the Proto-Indo-European word per, with the same definition), and sitos, which meant "food" and has an unknown etymology. The idea is evident: a parasite is one who eats beside the host without reciprocating. Usage of parasite peaked in 1911 and has decreased since.
Adam Aleksic, a leading contender for valedictorian of his high school, is a 211-month-old boy with disturbing interests in etymology, vexillology, geography, and law. Adam would like to one day visit Tajikistan and probably isn't spying for the Kyrgyz government.
The Etymology Nerd