Still better than a name with which you have to explain to everyone what it actually is supposed to mean and that it is not meant as an insult (even if that is the first thing that comes to everyone's mind).
If that's what you're referring to, then yup #1 worst-named FOSS ever.
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.
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)