> git, noun. British Slang. a foolish or contemptible person.
"Gimp" can be an ableist slur for someone with a walking impairment in US and Canadian English but also to someone engaging in BDSM (hence "gimp suit"). The GIMP project has also seen a fork in part due to conflicting opinions about whether the name should be changed (tho I think more people were aware of the BDSM meaning and felt uncomfortable with having sexual innuendos in professional software).
"Mongo" (in German, and presumably Dutch also, anyway) specifically is used to mock cognitive disability and is derived from the historical medical term "mongoloid" which in itself was already racist. Unlike git and GIMP it's also extremely likely none of the people involved in picking the name were aware of its unfortunate meaning since the name sounds innocuous in English.
The sexual term's etymology is the ableist slur. The gimp suit gimps you. It's the same thing.
Whereas in countries where "mongo" or some version thereof is a slur, for MongoDB it's racism -> ableism -> product name or even racism + ableism -> product name
The difference is subtle but IMO what makes it worse is that while "gimping" is a dismissive reference to disability, "mongo" is a slur directly mocking a person with a (real or alleged) disability. As I said, you wouldn't want to call your product "Ret*rdDB" either.
But I think arguing over which is worse misses the point: it's a good idea to check for foreign language implications when picking a name and you should avoid relying on juvenile puns.