I'm from Texas and "yeehaw" is a southern slang celebratory exclamation, so it's something people from outside the area kind of expect they might hear out here. It's maybe a bit rural and unsophisticated so you don't really hear it in casual conversation except rarely to be silly, but you see it enough in old movies depicting cowboys that most Americans are likely familiar with the word even though it's not regularly used.

When I heard about this server called beehaw, I thought it was just nonsense syllables. Then I saw the bee in the logo without really noticing the details and thought someone added a nonsense suffix to the word "bee". It wasn't until someone suggested members should be called the yeehive (which looks like hive with a nonsense prefix) and another commenter said they finally understand the server name that I took a closer look and noticed the cowboy hat and realized the name was from combining bee with yeehaw. Bees aren't really associated with cowboys, so it's not very obvious if you aren't looking for it. It's a pretty absurd amalgamation but the drawing of the bee in cowboy gear is adorable.