Thelyphonida is an arachnid order comprising invertebrates commonly known as whip scorpions or vinegaroons (also spelled vinegarroons and vinegarones). The name "whip scorpion" refers to their resemblance to true scorpions and possession of a whiplike tail. "Vinegaroon" is based on their ability when attacked to discharge an offensive liquid which contains acetic acid, producing a vinegar-like smell. Wikipedia