I love the fact that I've been doing etymological research for long enough to know where this word came from before I even searched it. Capricorn was first used in English circa 1400 CE in Geoffrey Chaucer's A Treatise on the Astrolabe and was either taken from French capricorne or directly from Latin capricornus, a word that literally means "goat-horned". This makes sense if you consider the symbol for the zodiac. Capricornus combines two words: caper, which meant "goat" (and derives from the Proto-Indo-European reconstruction kapros, defined as "buck") and cornus, which we've seen in cornucopia and unicorn as having meant "horn" (this comes from PIE kerh, also "horn"). Usage of the word capricorn peaked in the mid-eighteenth century and has since been trending downwards.
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.