It has no connection with those bounding marsupials of Australia. It means to pluck the wool from the fleece of a sheep. The word is closely associated with the crofting communities of Orkney and Shetland, though the technique is now rarely practised because it takes so long.
As you might guess from its heartland, it’s a Scandinavian term, brought to the islands by Norse settlers more than a thousand years ago, and which has modern equivalents in such languages as Norwegian and Icelandic. In such harsh northern climates, to shear sheep would be to put them at risk of dying from the cold and wet, even in summer. However, the local breeds naturally shed their old wool in the Spring as the new fleece grows out. With a lot of painstaking work that required nimble fingers, local women would pluck or roo the old wool close to the sheep’s skin as it grew out on various parts of the body.
The new fleece was left in place, providing protection for the skin against the elements. One of the advantages of this method was that the fibres, being uncut, had no sharp ends and so the spun wool was softer than that obtained by shearing.