If I'm not wrong sny is the plural accusative of sen, dream (m) So it should mean sweet dreams [This message has been edited by Kikko (edited 04-09-2003).]
Literally, it means "beautiful dreams". In Czech, there is an expression "Spi sladce" which means sweet dreams and is quite common as an epitaph on a grave. So we prefer to wish beautiful dreams to people who are still alive.
