Like, you can at least name it after another variant of Mango to make the name more interesting, or call it something similar but with a little more variation (like MangroveDB)
If that's what you're referring to, then yup #1 worst-named FOSS ever.
I only knew it as the name of "Planet Mongo", the main planet in the Flash Gordon universe, an old science fiction comic that has been rebooted many times (which also had loads of extremely racist anti-Chinese elements)
Though I do love the dictionary definition of "mongo":
"Items found in the trash that can be salvaged."
Sums up my views of mongodb pretty well, actually.
But like you, I have never heard "mongo" used in the same pejorative context.