"Circles"

    It was Girl Scout cookie season. The time of the year when those beautiful boxes of deliciousness were being sold everywhere, and when those who had a little sister selling the cookies got swarmed by masses.
    My math teacher mentioned the cookies during his lesson one day. Only he didn't call them cookies--he called them circles.
    Circles. For some reason, that was funny and surprisingly catchy. Cookies are delicious, but circles are amusing and delicious!
    Similarly, lots of characters in fiction use nickname terms for something. They give their vehicles names, refer to a favorite hangout to a cool-sounding term, and often in science fiction the technology and gadgets are given less formal names. "Sky Boat" is a whole lot easier to say than "anti-gravitational water vessel." Nicknaming things can also show a bit of a character's personality too if they're the one who made up the phrase. Someone who calls their car "the limo" is probably considerably different than a person who would call their vehicle "the Dude-mobile."
    Aren't nicknames like "circles" interesting? Do you use nicknames in your story, or in real life?