Comes from a now-inactive ancient Ruin machine.
The "Ruin" part of the name comes from the areas where they are most active. However, Ruin machines actually have little in common with the detritus in which they are often found.
In the ancient past, these ruins were once part of a civilization mighty enough to almost touch the dome of the firmament, while "ruin" still waits in the deep places of the earth, awaiting the order to arise and tread all kingdoms underfoot.