I could be wrong, but I believe it means: a wonderful (or beautiful) man (or woman) has left me.

There’s an explanation in German here:

http://www.hh.schule.de/GyCor/projekte/musik/uebersicht/html/afrikanische_musik.html

It looks like Sponono is a gender-neutral name (words for “man/woman/wife/husband” are completely different, and regular nouns always come with a noun class prefix which seems to be lacking here).

I found “yekile” translated as “left” and “abandoned” in a couple of sources, but the verb itself doesn’t seem to have any 1st person affix. So I think a purely literal translation would probably just be “Sponono left”.

Okay, yes, I found “ukuyeka” as an entry in an old EnglishKaffir dictionary meaning “to abandon,” so “yekile” is definitely an inflected form — “yek” is the root, the rest are affixes).

(Kaffir is an old name that referred to what are now separate languages/dialects of Xhosa, Zulu, etc.)

Isiponono (which can be pronounced sponono) may mean beautiful woman in Xhosa, but I can’t find any reliable confirmation. If I do I will add it to the dictionary.
Ukuyeka does mean to quit, to leave alone
“Isiponono sindiyekile” would mean “The beautiful woman left me”. That’s the closest to a grammatically correct sentence that I could make of this. Sponono yekile is not grammatically correct.

All in All the meaning behind the words (as bronz, fiosachd and Curtis explain the right details) is that one is finally free of someone. The energy of the song sounds like “yippie!! I’m free as can be!”
We do it in our choir and it’s a great song for individual improvisation. It makes me feel like a bird spreading its wings and taking off..