These are two words passed down from Latin and Greek origns.

CATASTROPHE: \Ca*tas"tro*phe\, n. [L. catastropha, Gr. ?, fr. ? to turn up and down, to overturn; kata` down + ? to turn.] 1. An event producing a subversion of the order or system of things; a final event, usually of a calamitous or disastrous nature; hence, sudden calamity; great misfortune.

DISASTER: \Dis*as"ter\, n. [F. d['e]sastre; pref. d['e]s- (L. dis-) + astre star, fr. L. astrum; a word of astrological origin. See Aster, Astral, Star.] 1. An unpropitious or baleful aspect of a planet or star; malevolent influence of a heavenly body; hence, an ill portent. [Obs.]