Adopted 3 December 1946 on Hydrographic Chart #3587 (now Chart #3567), as labelled on British Admiralty Chart 581, 1867 et seq, and BC Lands' map 2C, 1919; and identified in the 1930 BC Gazetteer.

Source: BC place name cards, or correspondence to/from BC's Chief Geographer or BC Geographical Names Office, file J.1.47

"Named in 1860 by Captain Richards**, RN, after Captain the Hon. John Wellbore Sunderland Spencer, RN, (1816-1888), HMS Topaze, on this station 1859-1863. Spencer was the 6th son of Francis, 1st Baron Churchill, who in turn was the youngest son of the 3rd Duke of Marlborough. Appointed Rear Admiral 1879; retired as Vice Admiral, 1874; later ADC to Queen Victoria." [** Walbran's attribution likely refers to the Mount Spencer, Mount Churchill, Marlborough Heights trio of names adjacent to Princess Royal Reach, Jervis Inlet - these features WERE named by Captain Richards in 1860 after Captain the Hon. John Wellbore Sunderland Spencer. The features in the vicinity of Topaze Harbour, Wellbore Channel and Sunderland Channel were named by Captain Pender in 1863, while conducting detailed surveys of the waterways on the north side of Johnstone Strait, and Capt. Pender likely named this particular feature Mount Spencer at the same time. Same namesake.]

Source: Walbran, John T; British Columbia Coast Names, 1592-1906: their origin and history; Ottawa, 1909 (republished for the Vancouver Public Library by J.J. Douglas Ltd, Vancouver, 1971)