mingus ah um No one else here took Latin in school?
Geez...
Well from what I remember (and I'm 99% certain of this), it's indeed a pun on a Latin grammatical concept.
Mingus is a "Latin-esque"-sounding name by virtue of the "-us" at the end... you know, like E Pluribus Unim ("Out of many, one."). Or Pastorius, for that matter (Latin for "shepherd," I believe).
So... what it looks like Charles did, was make up an imaginary Latin word (adj. in this case) -- Mingus. In Latin, that's the masculine form of the adjective. The feminine form would be "Minga" and the neuter form would be "Mingum".
So... in a Latin textbook, if "Mingus" were a real adjective, you'd see it listed like so:
Adj. -- Mingus, -a, -um.
Then, he took it, Anglicized it, and made it sound like someone mumbling.
Does that make sense? It's just a silly pun... but I would bet my next paycheck you'd never see anything that deep on a boyband title.
-a |