Brave New World's title derives from Miranda's speech in William Shakespeare's The Tempest, Act V, Scene I:
O wonder! How many godly creatures are there here! How beauteous mankind is! O brave new world, That has such people in't.—William Shakespeare, The Tempest, Act V, Scene I, ll. 203–206
This line itself is ironic; Miranda was raised for most of her life on an isolated island, and the only people she ever knew were her father and his servants, an enslaved savage, and spirits, notably Ariel. When she sees other people for the first time, she is overcome with excitement, and utters, among other praise, the famous line above. However, what she is actually observing is not men acting in a refined or civilized manner, but rather representatives of the worst of humanity, who betrayed or tried to betray their brothers or leaders to get ahead. Huxley employs the same irony when the "savage" John refers to what he sees as a "brave new world."
Translations of the title often allude to similar expressions used in domestic works of literature in an attempt to capture the same irony: the French edition of the work is entitled Le Meilleur des mondes (The Best of All Worlds), an allusion to an expression used by the philosopher Gottfried Leibniz and satirised in Candide, Ou l'Optimisme by Voltaire (1759).