The island is named after the three watermills that used to be on the island for beating copper and brass.
Daniel Defoe referred to the mills in his A tour thro’ the Whole Island of Great Britain (1724-1727).
He referred to the “three very remarkable mills, called Temple-Mills, for making Bisham Abbey Battery-work viz. Brass Kettles and Pans &c of all sorts. And these works were attended with no small success, till in the year 1720, they made a bubble of it; and then it ran the fate of all the Bubbles at that time”.
Learn about the Temple Mill Island history here.