Mongoose is an odd word. You would imagine it would have either a weird plural or at least an interesting one. It does not. Instead, the plural is "Mongooses" which sounds like a mistake when said aloud, and looks like one when written. Mongi on the other hand, seems like a word both when heard and read, and is weird enough to do Mongoose justice. But if you think that mongi makes drastically less sense than Mongooses, surely mongeese would be better than mongooses? After all, the plural of goose is geese. So whatever your tastes, it seems mongooses is a far inferior option for a plural than mongi and mongeese. Maybe if this gets enough signatures, others will agree.
http://twitition.com/a63p8/
