According to Strathearn School website: "Strathearn House was built in the 1864, on eighteen acres of land at Belmont, by William Mullan." It is highly likely the streets with the name Strathearn are called after this house/estate.
The name comes from Strathearn in Perthshire, Scotland. This is the valley of the River Earn, which flows into the Tay.
The name Strathearn Lane Off Circular Road was proposed by Carn Properties and approved by the Health and Environmental Services Committee, on Monday, 11th August, 2003.