My German is probably worse than yours, virtually zero, but it seems from that posting that Mjeto is the Sorbian for Martin. To me it looks more like a diminutive, or, to be honest, not like Martin at all. I've tried googling Martin and Mjeto together and got one other website that says Mjeto = Martin. I can't find anything on the web which deals with Sorbian names and their meaning.
Have you thought of putting a Miedecke page on genforum, where interested parties can exchange information? I should also mention, as you live in Australia, this website -http://www.wendishheritage.org.au/
Wendish is another name for Sorbian, less politically correct, but still used it seems. There is a list of names on there but Miedecke is not among them, so it may be that your forebears didn't start their migration to Oz from Sorb territory.
Finally, I should point out a mistake in my last posting. I wrote a name as Mietheck when it should have been Miethke.