It's because of the rubber duck methodology and in the early days we thought it would be cool to have a command `git duck` that starts a video to explain a commit.
Haha that's such a fun story!
I'll be blunt here, but I really do mean this in the spirit of constructive criticism: I hate the name. It's not related to Git in any meaningful way (why not "VimDuck" or "ZshDuck"?), and at first glance I'd assumed it had something to do with Cyberduck. Also, it doesn't exactly roll off the tongue: "hey, wanna hop on a Zoom?" flows better than "hey, wanna GitDuck?" Finally, the name pretty much limits it to only developers. Zoom was in a great place to capitalize on schools that were moving to remote classes, but "Zoom" doesn't really carry any semantic baggage. It would be awkward to explain to my boss why I wanted our company to your product for a business meeting, even if it's the perfect tool for it ("what's a git? What's it have to do with ducks?").