"anything that befalls of ruinous or distressing nature; any unfortunate event," especially a sudden or great misfortune, 1590s, from French désastre (1560s), from Italian disastro, literally "ill-starred," from dis-, here merely pejorative, equivalent to English mis- "ill" (see dis-) + astro "star, planet," from Latin astrum, from Greek astron "star" (from PIE root *ster- (2) "star").
The sense is astrological, of a calamity blamed on an unfavorable position of a planet, and "star" here is probably meant in the astrological sense of "destiny, fortune, fate." Compare Medieval Latin astrum sinistrum "misfortune," literally "unlucky star," and English ill-starred.
1580s, "ill-starred, unlucky," a sense now obsolete, from French désastreux (16c.), which is from désastre (see disaster) or else from Italian desastroso. The modern meaning "calamitous, ruinous, of the nature of a disaster," is from c. 1600. Related: Disastrously; disastrousness.
Proto-Indo-European root meaning "star." Buck and others doubt the old suggestion that it is a borrowing from Akkadian istar "venus." The source of the common Balto-Slavic word for "star" (Lithuanian žvaigždė, Old Church Slavonic zvezda, Polish gwiazda, Russian zvezda) is not explained.
It forms all or part of: aster; asterisk; asterism; asteroid; astral; astro-; astrobiology; astrobleme; astrognosy; astroid; astrolabe; astrolatry; astrology; astromancy; astronaut; astronomy; AstroTurf; constellation; disaster; Estella; Esther; instellation; interstellar; lodestar; star; stardust; starfish; starlet; starlight; starry; stellar; stellate.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit star-; Hittite shittar, Greek aster "star," with derivative astron; Latin stella, Breton sterenn, Welsh seren "star."
"disaster," 1848, from French débâcle "downfall, collapse, disaster" (17c.), a figurative use, literally "breaking up (of ice on a river) in consequence of a rise in the water," extended to the violent flood that follows when the river ice melts in spring; from débâcler "to free," earlier desbacler "to unbar," from des- "off" (see dis-) + bacler "to bar," from Vulgar Latin *bacculare, from Latin baculum "stick" (see bacillus).
The literal sense is attested in English from 1802, in geology, to explain the landscapes left by the ice ages. Figurative sense of "disaster" was present in French before English borrowed the word.
1530s, "reversal of what is expected" (especially a fatal turning point in a drama, the winding up of the plot), from Latin catastropha, from Greek katastrophe "an overturning; a sudden end," from katastrephein "to overturn, turn down, trample on; to come to an end," from kata "down" (see cata-) + strephein "turn" (from PIE root *streb(h)- "to wind, turn"). Extension to "sudden disaster" is first recorded 1748.