Nickname adopted with a certain perverse pride by the British 7th Armoured Division, stationed in Egypt and Libya in 1940, and later taken up by the entire Eighth Army fighting in the Western Desert campaign (against the Desert Fox, of course), and more recently by the 7th Armoured Brigade fighting in the Gulf War. The 7th Armoured's formation symbol is in fact a picture of a jerboa.
Another unfashionably short factual writeup from the "there's not that much to say but the gap needed filling" clique