Why is the ninth month called September?
late 14c., from Old French cristalin "like crystal" (Modern French crystallin), from Latin crystallinus, from Greek krystallinos "of crystal," from krystallos (see crystal).
crystalline crys·tal·line (krĭs'tə-lĭn, -līn', -lēn')adj.
Being, relating to, or composed of crystal or crystals.
Resembling crystal, as in transparency or distinctness of structure or outline.