E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
A spirit of the air and guardian of innocence. He was enslaved to the witch Sycorax, who overtasked him; and in punishment for not doing what was beyond his power, shut him up in a pine-rift for twelve years. On the death of Sycorax, Ariel became the slave of Caliban, who tortured him most cruelly. Prospero liberated him from the pinerift, and the grateful fairy served him for sixteen years, when he was set free. (Shakespeare: Tempest.)
Ariel. The sylph that watched over Belinda. (Pope: Rape of the Lock, i.)
Ariel. One of the angels cast out of heaven. The word means lion of God. (Milton: Paradise Lost, book vi. 371.)