I started off this post thinking about dictionaries, and words like likuta, plural mikuta (they used to be coins used in the former Democratic Republic of Congo, which is now Zaire). But I got side-tracked by a trail of magic.
Likuta is a Congolese word, and many people sold as slaves to the New World had Congolese as their native language; so while the Congolese language's home is still in Zaire, the Republic of Congo, and Angola (it has about nine million speakers altogether) Congolese-influenced languages are to be found in the New World. It's one of the sources of the Gullah language of the USA, and the Palenquero creole of Columbia.
Congolese also forms part of the ritual speech of Afro-Americans, especially in Brazil, Cuba and Haiti.
Hang on, I thought: ritual speech?
Well, the Congolese-influenced language we're talking about is Habla Congo, and it started off in Cuba. It involves deliberately switching between Congolese words, various forms of Spanish, and the creole of the Cuban slaves.
Habla Congo isn't a secret language, exactly - anyone is allowed to listen to it - but the idea is that no one who's not initiated can understand it.
Now, I'm not initiated, but I'll pass on something I found in Studies in Contact Linguistics: Essays in Honor of Glenn G Gilbert, in a piece by Armin Schwegler. It says that the language its speakers call the lengua conga is never spoken directly to researchers, but always to the altar, the spirit(s) or the sacred magic cauldron or nkisi.
...personally, I find I'm quite happy to leave some secrets exactly where they rest.
Word To Use Today: zombie. This is one of the few Congolese words that's come into English. Zumbi means good-luck fetish.