It is named after the civil engineer Robert Thom who designed the scheme which created the reservoir and delivered water via a long aqueduct known as The Cut.

From the northern arm an outlet feeds southwest a short distance to a compensation reservoir at the centre of the "C", which then connects at Cornalees Bridge to the start of The Cut.

The civil engineer Robert Thom from Rothesay prepared a scheme to turn this into a reservoir and create the aqueduct which became known as The Cut.

As shown in the picture of a restored mechanism, when the aqueduct is over full, water flows down the pipe in the foreground and fills the bucket, which then pulls the chain down over the pulley wheel and lifts the counterweight and the lever opening the sluice gate.

The cut provided a water flow to a series of falls running through water wheels powering various industrial processes, including a papermill, woollen and cotton mills, ropeworks, several sugar refineries, an iron foundry and shipbuilding works including production of steam engines and boilers.

From its opening, the nearly level footpath formed on the embankment to the downhill side of the aqueduct proved a great attraction, and "walking the Cut" continues to be popular.