Q: When did the “e” disappear from “disastrous”? In other words, why don’t we spell it “disasterous”?
A: English borrowed both the noun and the adjective from French, according to the Oxford English Dictionary.
The source of the noun was désastre while the source of the adjective was désastreux (masculine) and désastreuse (feminine)
However, both “disaster” and “disastrous” are ultimately derived from astron, Greek for star and the source of the English word “astronomy.”
Etymologically, according to John Ayto’s Dictionary of Word Origins, the underlying meaning of the adjective is ill-starred and of the noun a “malevolent astral influence.”
The adjective, which showed up in the late 1500s, was originally spelled “desastrous” or “dysastrous.” Although an “er” version, “disasterous,” showed up briefly in the early 1600s, it didn’t catch on.
The earliest example in the OED is from Ciuile Conuersation, a 1586 translation of a work by the Italian writer Stefano Guazzo about economics and society:
“If she aford mee but one sparkle of hope and favour, she doth it to no other ende, but to make mee more desastrous.”
The noun, which first appeared in the early 1600s, was spelled “disaster” from the beginning. Shakespeare, who used it in seven of his plays, was probably responsible for popularizing the Anglicized spelling of the French noun.
The OED’s earliest example is from Hamlet (1604): “Starres with traines of fier and dewes of blood / Disasters in the sunne; and the moist starre, / Vpon whose influence Neptunes Empier stands, / Was sicke almost to doomesday with eclipse.”
Why, you ask, is the “e” in “disaster” missing from the modern adjective “disastrous”?
We suspect that the pronunciation of the adjective in French may have influenced its spelling in English. And Shakespeare’s decision to Anglicize désastre as “disaster” probably influenced the spelling of the noun.
from Grammarphobia http://ift.tt/1RCvd4b