Castalia

An unexpected route to nicknames Cassie or Cass, Castalia was the name of a river nymph in Greek mythology. She gives her name to the Castalian Spring, near Delphi, whose waters are said to have been either a gift to her from the river Cephisus or to been named for her, after she flung herself into the waters and became a fountain to flee the advances of Apollo.

Connected to poetic inspiration and cleansing, the exact etymology of the name is unknown, though theories include that it comes from katharos meaning "spotless, pure" or kassuo meaning "to sew, to stitch"

Pronounced kuh-STAHL-yuh.

As of October 2026, Castalia ranked #15765 for girls in US births in 2022 SSA.