1550s, from Middle French cube (13c.) and directly from Latin cubus, from Greek kybos a cube, a six-sided die, vertebra, perhaps from PIE root *keu(b)- to bend, turn..
The triangle illustrates the three elements a fire needs to ignite: heat, fuel, and an oxidizing agent (usually oxygen). A fire naturally occurs when the elements are present and combined in the right mixture, meaning that fire is actually an event rather than a thing. A fire can be prevented or extinguished by removing any one of the elements in the fire triangle. For example, covering a fire with a fire blanket removes the oxygen part of the triangle and can extinguish a fire.
Fire needs three elements to prosper: fuel, oxygen and heat. The most common extinguishing agents like water, carbon dioxide, dry chemical and foams attack the fire physically to deprive the fire of one or more of the three critical elements needed for propagation. Halon differs in the way it puts out the fire.