David Saunders and Jim Poole counting the burrows of Manx Shearwater (Puffinus puffinus) and Puffin (Fratercula arctica) on Middleholm in February 1998.

The name Middleholm was documented in 1325 in the reign of Edward III, when ferreters were paid for catching rabbits. The island has been in use for considerably longer, with traces of Iron Age walling, and may have been used for summer grazing, despite the lack of natural fresh water. Since 1966, when the rabbit population was killed by myxomatosis, the island has been ungrazed.
The name Midland Isle has been used at least as far back as 1578, when it was abbreviated in Latin as Midlan Insul. This name was also used in 1833, when it was cited in Lewis's A Topographical Dictionary of Wales. Modern Ordnance Survey maps use the latter name.