Cassandra Trelawney

Cassandra Trelawney was a famous, celebrated witch and Seer. She was the great-great-grandmother to Hogwarts School of Witchcraft and Wizardry Divination Professor Sybill Trelawney. She possessed the Inner Eye, which was passed on into generations later.

Behind the scenes

 * "Trelawney" must have been Cassandra's married name. If her maiden name was Trelawney, then Sybill Trelawney's surname would not be, as it would be whatever the surname of Cassandra's husband was. Alternately, Cassandra might have been a single mother/may have not taken her husband's name.

Etymology
Cassandra is generally taken to mean "she who entangles men". This meaning came from the Greek culture and was translated to mean various other things as well; such as "oracle".

In Greek mythology, Cassandra was a princess of Troy. Her beauty caused Apollo to grant her the gift of prophecy. However, when she did not return his love, Apollo placed a curse on her so that no one would ever believe her predictions.

Appearances

 * Harry Potter and the Order of the Phoenix
 * Harry Potter and the Half-Blood Prince