Guanabana / Guayabana
Hmm, that's hard to say. It may all be a problem of spelling! The first one is definitely spelled right and is the same as the soursop (in english speaking countries) and graviola (in portugeuse/brazil). It is large, green and soft spiny outside with white melting slightly grainy flesh that surrounds many dark black smooth seeds. And it's delicious! I get a smoothie of it whenever I see it and I had sorbet made from it nearly every day in Brazil.
The latter is most likely a misspelling for either Guanabana (which seems common on a quick search on the internet) or Guayaba (the spanish for guava). There is one fruit in Peru called Guayabana that is related to Guanabana/Soursop/Graviola, but this is extremely uncommon and not likely to be what you're talking about. See here: http://sisbib.unmsm.edu.pe/BVrevistas...
I'm an ethnobotanist and I've had over 200 species of fruit in my life (yes, I keep a list!) and I've never had that one and I've done research i the Peruvian Amazon where I ate plenty of wild fruit.
Can you give us some context? Where did you hear these words? Were they attached to particular fruit that you or a friend ate? Any more explanation would help clear it up. But this is the kind of mysteries I love to clear up about fruit!
I bought a can of the guanabana nectar to use in a cocktail and a friend who is cuban insisted i was mispronouncing it.... he said it's guaYabana, not guaNabana, despite the spelling on the can indicating otherwise. I told him I though he was wrong and well.... now we have a bet.
I tried googling, but did not find a clear answer.
re: echo eater
I'm cuban and there's definitely a fruit called a guanábana. It's pronounced exactly as it's spelled, with the accent on the NA syllable (gwa-NA-bana). It's green and spiny on the outside with a white creamy inside. Guayaba (gweye-aba) is guava, a totally different fruit. Both grow in Cuba. Your friend is mistaken.