Good days, because the truth is that has uns etymology very curious, comes of the expression Latin ' Sit tibi terra levis', that is placed in them epitaphs of the tombstones mortuary, and means: that (the weight) of it land you is mild (light)Is currently used to want someone who is going to have a day or complicated task, which best help it
Expression of mood and farewell from someone whom we wish luck and success to a more or less difficult task. This all expression recalls that one used as an epitaph in the pre-Christian Roman world that recorded on the gravestones as acronym: S.T.T.L. Sit Tibi Terra Levis. That the Earth is slight, locution that with different variants also used the Roman poets, as Tibullus: terraque securae super sit ossa levis: that the land of the inexorable is light on your bones.
