Five hundred years ago, we didn't have a word for mosquito. The early speakers of Modern English had to make do with terms like gnat or midge, but those weren't perfect because they referred to multiple kinds of insects. That's why we turned to the Spanish in the late sixteenth century and simply borrowed their word for "gnat", mosquito. This was possibly adopted by American colonists near the Spaniards in Florida, through English trading with continental Europe, or by another medium - we're not really sure. Mosquito is a diminutive of Spanish for "fly", mosca, and that's from Latin musca, with the same definition. Further back, that may derive from the Proto-Indo-European reconstruction mew, which is also thought to be the distant etymon of midge. We've come full circle!
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.