Thank you for your interest! I am intrigued, do you have a connection to the name or the area? Anyway, I'm very sorry for the delay in replying. I only just found your comments.
Yes, 'Svombo' (plus variants) is an unusual name. I'm fascinated by it.
My gt gt grandfather was, indeed, the Nicholas Svombo who married Ellen Barry. They had a lot of children, including my gt grandfather, Constantine.
I haven't actually found any records for Nicholas, prior to his arrival in the British Isles, but there are records of a Svombo family on Hydra. I'd love to research them, but my Greek isn't good enough. A Svombo lady did transcribe some of them for me.
I do have several family photos ~ including one of Nicholas ~ and the connection certainly looks more Mediterranean than Scandinavian. My grandmother, for example, had black hair and black eyes.
A cousin did actually suggest a Scandinavian connection, when he saw a similar name on a Scandinavian cheese ~ and I did try to check into that surname. (Indeed, there are quite a few similar surnames in Northern and Eastern Europe and some may well be connected to us and to each other.)
I seem to recall ~ and I may be wrong ~ that the Scandinavian 'Svabo' came from 'swan farmstead / homestead', while Svobo / Svobos / Svoboda / Sloboda etc, (+ possible Svombos) as you said, come from the Slavic word for 'freedom'.
I contacted some prople, at universities in the Balkans, and was given a few ideas. It's possible that names like Szambo, Szabo, etc, are also connected in some way. One suggested a possible link with Schwabien / Swabia in Germany. Looking at the Ellis Island records I have found quite a lot of potentially related names.
Whatever his ancestral origins, though, my great great grandfather definitely seems to have come from somewhere in Greece. That is how he is described in records. The whole family considered themselves to be part Greek. My late Uncle said that the name wasn't originally 'Svombo', but was more like 'Gzombos' ~ ie Svombos.
Once I started searching modern records for the surname 'Svombo', I found some people with the same name on the Greek islands of Hydra and Spetses, and some in Piraeus on the mainland. There aren't many of them. There are also a few in America ~ plus, of course, 'ours' in the British Isles.
Interestinly, one of the men mentioned to me, by my Hydriot friend, from her Mayoral records, seems to be recorded on the English census, as a sailor from Idra. (I think that this was in 1881.)
There is another family, with a very similar name, who are from Northern Greece, near the Albanian border ~ Albania being the place where many Hydriot families originated.
Apart from those in Northern Greece near Albania, the others all seem to originate in Hydra ~ the island of refugees.
I think that I once found a 'Swomboda' in the USA, and there are some others with similar names, but I don't know anything about them. (Just to confuse matters, there are also some very similar African and South Asian names.)
Though 'Svombo' etc is rare, 'Svobo', 'Svoboda', etc, etc, are not at all rare. There are lots and lots of people with such names ~ especially in the Balkans, but also all over the world, it seems.
You are right that in Greek the name is written 'Σβομπος'. The Hydriot lady I wrote to, with that name, said that it could be transcribed as Svombos, Svompos or Svobos and all were the same name ~ and, yes, Svobo relates to 'freedom'. I think that the form pronounced 'Svombos' is likely to have been a local pronunciation of 'Svobos'. (I used to wonder if fleeing refugees might actually have symbolically taken on the name 'freedom'. It's possible, I imagine.)
I am wondering why some of my Greek contacts have said that the 'mb' sound does not feel Greek, because I have found other Greek words, which seem similar to me. I shall have to ask someone, when I can.
I really don't think that there was a French connection, regarding this surname (as a seafaring man Nicholas may have been there, though) since the name is still pronounced that way in Greece (ie. Hydra and North Epirus) and Greek friends pronounce this name ~ 'Σβομπος' ~ as Svombos. I do think, though, that, when spoken by a Greek person, Svombo and Svobos would sound very similar.
It remains intriguing and mysterious, and I shall be interested in any of your findings that might shed more light on the history of this name.
I would like to know more about any families, who may have a version of 'Svobo', etc, that includes the 'm' sound, as our version does.