What does Charis mean?
From Greek 'charis' (χάρις) meaning grace, kindness, or charm. In Greek myth the Charites (Graces) were goddesses of grace and beauty; the root also underlies the word charisma.
What does Charisse mean?
Generally a French-styled elaboration of Greek 'charis' (grace, kindness). Some sources propose an unrelated derivation (a cherry/Latin 'ceresia' link, or a feminine of Charles), so the grace meaning is the most-cited but not undisputed.