I have searched long and hard for the origins of the woggle and the meaning of its name: its origins seem to be purely in Scouting (and by derivation, Guiding) and the original Woggle was a two-strand Turk's Head knot made out of a leather thong. (Lord Baden-Powell reputedly kept a leather thong given to him as a good luck token just days before the relief of Mafeking.) The name "woggle" is believed to be word invented by Francis Gidney, Gilwell's first Camp Chief.
Whether or not all this is true I have no way of knowing. Although the Turk's Head Knot woggle remains popular, many other styles have arisen and many unique woggles made. (Woggles are also known as "slides," particularly in the USA.)
Instructions for the Turk's Head knot can be downloaded here (right-click and select Save Target As...)
To see how to plait (or re-plait!) a three-strand "endless" leather woggle (below), click here.
For how to fold a necker to use with a woggle, see this page.