[1] The Willis Islands were charted in greater detail and individually named by Discovery Investigations (DI) personnel between 1926 and 1930.

On that basis, the UK Antarctic Place-Names Committee (UK-APC) recommended the present shortened form of the name.

Acorn Rock rises 20 m (66 ft) above sea level, 0.35 mi (0.6 km) northwest of Main Island.

[12][4][13] The existence of the passage was first reported in the 1930s, and confirmed by HMS Owen during a hydrographic survey of the area in 1961.

It was descriptively named by UK-APC, the expression "standing proud" in naval parlance being the equivalent of "sticking up.

[17] This article incorporates public domain material from websites or documents of the United States Geological Survey.