Mech is the common abreviation for Mechanical Combat Unit, and refers to a wide-range of machines, entailing a piloted automaton of some recognizable shape.
Anecodotal evidence and secondary sources indicate that mechs were used in Antiquity, though no details survive. When all known technology was destroyed at the Fall of Roads, mech-building was completely lost.
Machines described as mechs were built and employed as far back as the Mage Wars. Some of these were Magic-Tech inventions, while others were pure technology. As civilizations rose and fell, many designs were invented and lost, only to be rediscovered centuries or millenia later. These devices came to be known as "New-Types" as they may have been technologically superior to modern designs.
Curiously enough, the fabled Gudersnipe Army was not known to have used Mechs during the Mage Wars. The Iron Reavers may be understood as mechs; but are classed separately.
The massive demilitarizations that followed the war destroyed much of mech technology, with few designs constructed or employed through much of the Golden Age, up until the ninety-nine-years war. Later mech appeared in the Kamian Succession Wars.