It is composed of two roots: dis and aster. Dis in the Latin variously means apart, opposite, deprive, exclude or expel. For example, disabled means to be deprived of certain abilities, to disbar means to expel from the bar, disarray means the opposite of array, and so on. The root aster comes from astro, meaning a star, or stars. The meaning for the prefix dis that most pertains to the word disaster is expel, implying an association between an event bringing about great damage and destruction and something expelled from the stars!