Cassandra f. Greek Κασ(σ)άνδρα, of uncertain etymology. The second element is derived from Greek ἀνήρ 'man'. de Felice s.n. Cassandra suggests that the prototheme is pre-Greek *kad- 'excel'.
In Greek mythology, the name of a daughter of King Priam of Troy and famous prophetess.
The name first came into use in England in the 12th C, a period where many fanciful names of Greek and Latin origin were introduced or coined. Many of these names remained in use only a century or two, but Cassandra appears again in England in the 16th C. In Italy, the name was introduced as part of the general revival of classical names in the Renaissance.