Girls

Rosella can be seen as a nature name (a rosella is the name of a variety of beautiful Australian cockatoos and an Australian flower) or a diminutive version of Rose.

Seneca was both a Roman philosopher-statesman and is a Native American Iroquois tribe. Occasionally used for both girls and boys, Seneca is now a Hunger Games character.

Signy — also spelled Signe — would make another distinctively offbeat alternative to Sydney. Signy appears in Norse mythology as the twin sister of Sigmund.

Actress Sigourney -- born Susan -- Weaver made this unusual name (which she found in The Great Gatsby) famous, if not popular.

Less popular than the Bueller-inspired Sloane but following on its coattails, this name ranks toward the middle of the Top 1000, but we see both spellings sticking around for years to come.