I'd like to add, two years later, that the idea of 'switching' can be misleading when discussing Swedish word order. The thing is that in main clauses, the verb goes second. And in questions it goes first. But it doesn't necessarily follow that anything is 'switched', because the subject doesn't necessarily go first in a main clause. It usually does in a short sentence like Jag ska upprepa because there's not much else to choose from, but in longer sentences, we might well have something else we want to put first, like I morgon ska jag upprepa 'Tomorrow I will repeat' – and then the subject goes after the verb. Because the only thing that really matters is that the verb goes in second place.
Yesterday I listened (stand by) to somebody who was having a phonecall. His told his phonenumber through the phone, and then asked to repeat the number (so he understand it right), he used the word "repetera" as he asked to repeat it. But now I understand that this native swedish man is wrong and he had to use "upprepa"? I do not understand.
Yes and no... it's a but of a grey area, to be honest. Ten years ago, I would have said that he was absolutely wrong. Five years ago, I would have said that it's too colloquial but does exist. Today, I'm leaning towards that it's still colloquial but obviously gaining in acceptance.
If you use repetera like that in edited text, you will no doubt be asked to change it. But in everyday language, the border is much less clear.
There isn't actually a completely obvious etymology here. The first part is easy: upp can serve as a particle to signify something being opened.
However, the second part is trickier. Ultimately, it comes from a Proto-Germanic root, in turn derived from Sanskrit that has many, many descendants in various languages. The original meaning was to touch or graze something.
Words that may be related include the Swedish word for "scratch", repa, and the archaic rappa which means to carry off and which may or may not be a cognate of the English "rape". We also have rippa in Old Swedish, meaning to "lift" or to "set into motion".
The more direct etymology is that it's borrowed from Middle Low German upreppen, with the same meaning - to bring something forward again.
I'm not sure if that actually helps at all, but unfortunately this is not one of those cases where it's easy to follow exactly what happened.