You’ve noticed something very important: there’s no natural reason for the words humans use. Any sound could be used to describe a big mammal that eats berries and salmon.
But people who speak English choose “bear.” People who speak Spanish use “oso.” People who speak Maricopa say “maxwet.” They’re all different, but they’re all correct.
That’s what I learned from my friend Lynn Gordon, an associate professor emeritus of linguistics in the English department at Washington State University.
“Why do we call bears ‘bears’?” she said. “Because we’ve agreed to.”
Humans have a unique knack for speech. They talk about things in the past or future. They make up new words. They even say things they’ve never said before (like you did with your excellent question).
To be understood, speakers of a language agree about its rules. This happens very early, when a baby is first learning to talk.