Why is the ninth month called September?
the muse of the dance, Greek Terpsikhore, literally "enjoyment of dance," from terpein "to delight" (from PIE root *terp- "to satisfy;" cf. Sanskrit trpyati "takes one's fill," Lithuanian tarpstu "to thrive, prosper") + khoros "dance, chorus" (see chorus).
in Greek religion, one of the nine Muses, patron of lyric poetry and dancing (in some versions, flute playing). She is perhaps the most widely known of the Muses, her name having entered general English as the adjective terpsichorean ("pertaining to dancing"). In some accounts she was the mother of the half-bird, half-woman Sirens, whose father was the sea god Achelous or the river god Phorcys.