Daughter of the banished duke, but brought up with Celia in the
court of Frederick, the duke's brother, and usurper of his dominions.
When Rosalind fell in love with Orlando, Duke Frederick said she must
leave his house and join her father in the forest of Arden. Celia
resolved to go with her, and the two ladies started on their journey.
For better security, they changed their names and assumed disguises;
Celia dressed herself as a peasant-girl, and took for the nonce the
name of Aliena; Rosalind dressed as her brother, and called herself
Ganymede. They took up their quarters in a peasant's cottage, where
they soon encountered Orlando, and (to make a long tale short) Celia
fell in love with Oliver, the brother of Orlando, and Rosalind obtained
her father's consent to marry Orlando. (
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894
More on Rosalind from Infoplease: