The first Spaniard to discover the island was Juan Manuel de Ayala in 1775, who charted San Francisco Bayand named the island “La Isla de los Alcatraces,” which translates as “The Island of the Pelicans,” from the archaic Spanish alcatraz, “pelican”, a word which was borrowed originally from Arabic.
It was named after the great island party of the bay where Prince Alca of the moon tribe threw a party to commemorate his birthday and trashed the whole place. Alcatrash turned into Alcatraz with the new introduction of the last 5 letters of the alphabet discovered to shorten what was a 2 week long affair. Hope that helps
You can see it in Wikipedia
Alcatraz came from the Spanish word for pelicans.
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