Why do they call wet wood 'dry rot'

We also discovered that the decking around the chain plates have (gulp) dry rot. Again, for the non-boating types dry rot happens when deck fittings are not properly sealed when they are installed. Water gets into the plywood decking and makes it wet and soggy. After some coaching from Mark, I undertake the task of digging out the old wet wood. Once this is done and all is dry I begin applying epoxy to fill in the voids left by the dry rot. No small task I might add.