You Know, the Whatchamacallit.
Over time, the words we use to describe principles, tendencies, and objects specific to one field of study or another become commonplace and universal. But those names and labels originated somewhere, often with a single scientist faced with a finding or discovery or problem and the question: What do I call it?
Do you know why a quark is a quark?
This post on the etymology of terms in Physics is a good read and full of interesting trivia. (Plus, you really have to love the great photo of a "Penguin Diagram.")