A tregging is no leggings and no pants
A tregging originates from the words trousers (in Dutch plain pants) and leggings. It is therefore a combination of leggings and pants and is usually somewhat thicker, stiffer, tighter than a legging. In the same context, you also have the word jegging. A jegging is then again the jeans form of a legging.
Images of Treggings and jeggings