Till – An unsorted mixture of sand, clay and boulders carried by a glacier and deposited as ground moraine over a large area

If you tilt (till) out all the sand, clay and boulders over a large area it looks like ground moraine.

Till is material deposited by glacial ice over wide areas. It is sometimes called boulder clay because it is mostly made up of clay and boulders, or a mixture of these. 

Till comes from the erosion of material caused by the movement of a glacier. It forms lateral, medial and terminal ground moraines.