Halcyon (Ἀλκυών) comes from the Greek alkyōn, meaning "kingfisher." In Greek myth, Halcyone was transformed into a kingfisher with her husband Ceyx; the "halcyon days" of calm weather around the winter solstice are when she nests.
Halcyon is rare as a given name but distinctive.
Halcyon reduces to seven — the number of mythical calm.