[2] The area was charted by the Belgian Antarctic Expedition (BelgAE) under Adrien de Gerlache, 1897–99, the French Antarctic Expedition (FrAE) under Jean-Baptiste Charcot, 1903–05 and 1908–10, and the British Graham Land expedition (BGLE) under John Rymill, 1934–37.

The names Argentine, Roca and Cruls were variously applied to the four island groups on the south side of French Passage.

The islands were mapped in detail by the Falkland Islands Dependencies Survey (FIDS) from photographs taken from the helicopter of HMS Protector and from information obtained by the British Naval Hydrographic Survey Unit in 1958, and the three names positioned as originally given by the Belgian and French expeditions.

The remaining island group was named Anagram Islands by the UK Antarctic Place-Names Committee (UK-APC) in 1959, anagram meaning a transposition of parts.

So named by the UK-APC in 1961 because there is a black knob of rock, almost permanently snow free, on the north side of the island which is a useful navigational mark for vessels using French Passage.