The name was very popular until the 15th century in England, usually in the vernacular form Maud. Both forms were revived by the 19th century. This name appears in the popular Australian folk song Waltzing Matilda, written in 1895.
Princess of the Land of the Green Isles and the protagonist's (your character's) love interest, she is one of the main co-characters in the sixth installment of this series, "Heir Today Gone Tomorrow."
The name Cassima more than likely originates from the masculine Arabic name Qasim, as her homeland seems to share many similarities with Arabic culture, as seen in architecture and dress, and the meaning of the name Qasim fits a description of the characters personality and values very well.
Other possible origins of this name include Cosima or an alteration of some Cass- name, such as Cassandra.
This name was borne by the heroine of Lewis Carroll's novels Alice's Adventures in Wonderland (1865) and Through the Looking Glass (1871).
In Britain the parallel form Alice, derived via Old French, has historically been more common than Adelaide, though this form did gain some currency in the 19th century due to the popularity of the German-born wife of King William IV, for whom the city of Adelaide in Australia was named in 1836.