A phantom island called Brasil or Hy-Brasil is said to lie close to which country?

To the west of Ireland is a phantom island said to lie in the Atlantic Ocean. Irish myths described it as cloaked in mist except for one day every seven years, when it became visible but still could not be reached. The etymology of the names Brasil and Hy-Brasil is unknown, but in Irish tradition it is thought to come from the Irish Uí Breasail (meaning "descendants (i.e., clan) of Breasal”), one of the ancient clans of northeastern Ireland. Í: island; bres: beauty, worth, great, mighty.

Despite the similarity, the name of the country Brazil has no connection to the mythical islands. Nautical charts identified an island called "Bracile" west of Ireland in the Atlantic Ocean as far back as 1325, in a portolan chart by Angelino Dulcert. Later it appeared as Insula de Brasil in the Venetian map of Andrea Bianco (1436), attached to one of the larger islands of a group of islands in the Atlantic. This was identified for a time with the modern island of Terceira in the Azores.