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.
"On the recommendation of the city surveyor, the committee approved of a proposal of McFarland Bros Limited to name a new street off Circular Rd, Strathearn Park". (5th May 1959).