Like Salisbury Street off Dublin Road, Salisbury Avenue is named after Robert Gascoyne-Cecil, 3rd Marquess of Salisbury, a Conservative statesman who was vehemently opposed to Home Rule for Ireland (John J. Marshall, Belfast Telegraph 03/03/41). He was Prime Minister of the United Kingdom for three separate periods for a total of over 13 years between 1885 and 1902. His three terms as Prime Minister were interrupted by Liberal governments led by Gladstone. There was considerable opposition to Home Rule in Belfast at that time.
The southern section of this street was originally called Fortwilliam Street. It was then changed to Kenbella Avenue in 1876. Somewhat confusingly, the northern end was named North Circular Road, although there is no overlap between that section of road and the current North Circular Road. The name of the middle section was changed again in 1890 to Salisbury Avenue, and in 1895 this name was adopted for the street's entire length.
There was, in fact, a proliferation of Belfast street-names honouring the Marquess of Salisbury at the end of the 19th century. As well as Salisbury Street in BT7 (and the adjacent Salisbury Court, created later), there was a second Salisbury Street in Ligoniel, which was later renamed Lever Street to eliminate the duplication of the name.
"Moved by Councillor Matthews, seconded by Councillor Shaw, and resolved that the resolution passed on 3rd Inst., altering the name of the street hitherto known as Salisbury Avenue to Kenbella Avenue, be rescinded. Moved by Councillor Matthews, seconded by Councillor Shaw, and resolved that the Council be recommended to have the street from Antrim Road to Old Cavehill Road, a portion of which was hitherto known as Kenbella Avenue, named Salisbury Avenue". (17th December 1901).