Hello Tricia. This is an intriguingly rare surname! I've read your other post in 2007 and about the Greek origin, and that Svombo could not be pronounced in Greek. Well, I was searching for the possibility of a Scandinavian origin and I came up with something very interesting. I know that you spent a lot of time researching this surname, this could be interesting.
I looked up a similar surname, Svabo, and according to http://lastnames.myheritage.com/last-name/Svabo , most of the bearers are from Faroe Island! Now Faroe Island is north of the UK, similar to Shetland and Orkney of Scotland. I went in deeper and founded the Norwegian surname Svabø. This probably explains the Svabo of Faroe Island, as they are of Norwegian origin. When the name Svabø is pronounced, it sounds almost identical to "Swambo"! This explains why the surname Swambo changed, and if Swambo is a variant of Svombo, then perhaps Svombo is a variant of Svabø! So, there is a possibility that your surname Svombo/Swambo could have originated from Norway, and it was originally Svabø.
But I want to clarify this. I've also seen your other posts on other sites and that you traced your great great grandfather from Greece. Is your great great grandfather Nicholas Svombo?, the one who married Ellen Barry? and did you actually traced Nicholas Svombo from Greece? as he actually once lived there? If so did you find any records of him in Greece?