The term Landcrab, or to be more precise, Giant Landcrab was, to the best of my knowledge, dubbed by a journalist in the UK. He was watching them going through their paces at the Army's tank training course at Bagshot. Using binoculars, the impression as they were weaving through the mud was indeed, that of a large crab. It's now become a term of endearment, so much so that the large club catering to all 1800s and its derivatives is called The Landcrab Owners' Club.