Rocabarra or Rocabarraigh is a phantom island

Phantom island

Phantom islands are islands that were believed to exist, and appeared on maps for a period of time during recorded history, but were later removed after they were proved to be nonexistent...

 or rock in Scottish Gaelic myth, which is supposed to appear three times, the last being at the end of the world.

"Nuair a thig Rocabarra ris, is dual gun tèid an Saoghal a sgrios".

The name confusingly has also been used to refer to Rockall

Rockall

Rockall is an extremely small, uninhabited, remote rocky islet in the North Atlantic Ocean. It gives its name to one of the sea areas named in the shipping forecast provided by the British Meteorological Office....

, a real rock in the North Atlantic. For example, when Martin Martin

Martin Martin

Martin Martin was a Scottish writer best known for his work A Description of the Western Isles of Scotland . This book is particularly noted for its information on the St Kilda archipelago...

 visited St Kilda

St Kilda, Scotland

St Kilda is an isolated archipelago west-northwest of North Uist in the North Atlantic Ocean. It contains the westernmost islands of the Outer Hebrides of Scotland. The largest island is Hirta, whose sea cliffs are the highest in the United Kingdom and three other islands , were also used for...

 in 1716, he refers to it as Rockoll, but goes on to mention that the locals also knew Rockall as Rockabarra (Rocabarraigh).

The name has hints of a Norse origin, barraigh (bar-ey) being a common element in Scottish placenames. Roca may come from the Gaelic

Goidelic languages

The Goidelic languages or Gaelic languages are one of the two branches of the Insular Celtic languages, the other consisting of the Brythonic languages. Goidelic languages historically formed a dialect continuum stretching from the south of Ireland through the Isle of Man to the north of Scotland...

rocail meaning crashing or roaring.