Well, it's not completely accurate. (My father was from a town near Naples. I learned a bit of dialect from him, and from a visit there.)

"Jammo ncoppa," pronounced more or less YAM-mah in-COPE-a or YAM-mah 'n-GOPE-a, means "Let's go up to the top," or "Let's go up there."

So that the translation "Let go on, let go, let go" was presumably supposed to be "Let's go on [the funicular], let's go, let's go."

That offensive-sounding "baby" isn't translating anything that appears in the song at all, it's just thrown in by the translator to indicate that the song is being sung to the lady he [the singer] is in love with. Unrequited, apparently. Well, very few Neapolitan love songs are about requited love.

I have usually heard the chorus as "Iammo, iammo, Iammo ncoppa la (twice), Funiculi funicula (twice) Iammo ncoppa la Funiculi Funicula." Not very different but different. Iammo and Jammo are equivalent. And it does usually sound like Yammah, not Yammo.

For what it's worth: I have a book of Italian songs that gives the start of the first verse as
"Stasera, Nina mia, io son' montato (che lo diro'? che lo diro'?)
Cola' dove mi aspetta un cor ingrato (piu' far' non puo, piu far' non puo."

i.e. This evening, my Nina, I went up (what shall I say to you, what shall I say about it....)
Up there where an ungrateful heart waits for me (I can do no more, I can do no more.)"

The chorus goes (forgive spelling errors, from memory right now) "Lesti, lesti, Gia' montiam' su la, lesti, lesti, gia' montiam su' la, Funiculi Funicula etc."

Don't know what Lesti means but "Gia montiam' su la" means [right now? Literally gia' is already] let's go up there [by funicular railway.]

Sorry, this is a bit mixed up. Tired but couldn't resist when I saw this thread.

Rita Ferrara